hckrnws
The most amusing tidbit about the tz database is that it contains an estimate of Big Bang, and it refuses to calculate timezone transitions occurring before the Big Bang.
The commit message at https://github.com/eggert/tz/commit/b22d459a367f4d01b10f6f6b... says:
> For example, Glib computes Sao Paulo time stamps as if Brazil's circa-1913 rules were still in effect. (Thanks to Leonardo Chiquitto for reporting the bug.) Work around the bug by not generating time stamps equal to -2**63. Come to think of it, time stamps before the Big Bang are physically suspect anyway, so don't generate time stamps before the Big Bang.
Soon afterwards, a separate commit disallowed leap seconds before the Big Bang.
There used to be a long manpage about linux/unix `date` and what dates meant in the past - with examples of 15 century and so. Talking about some king who liked some week/month and decreed it must be repeated, and another who disliked some week and scratched it off the calendar.. It was very eye-opening reading.
But i can not find it anymore. Anyone has an idea ? Is it gone completely?
man cal:
Two different calendar systems are used, Gregorian and Julian.
These are nearly identical systems with Gregorian making a small
adjustment to the frequency of leap years; this facilitates
improved synchronization with solar events like the equinoxes.
The Gregorian calendar reform was introduced in 1582, but its
adoption continued up to 1923. By default cal uses the adoption
date of 3 Sept 1752. From that date forward the Gregorian
calendar is displayed; previous dates use the Julian calendar
system. 11 days were removed at the time of adoption to bring the
calendar in sync with solar events. So Sept 1752 has a mix of
Julian and Gregorian dates by which the 2nd is followed by the
14th (the 3rd through the 13th are absent).
no, not that. It was like 5-10 full pages, talking about history, mostly western european but not only..
Honestly, that seems quite practical — it's a good way to head off "angels dancing on the head of a pin"-style arguments between contributors.
Another way to put the bug outcome is: "Instants before the Big Bang are out of scope of this library, so if an algorithm produces incorrect values, but only before the Big Bang, the algorithm is acceptable and does not need to be improved/replaced."
This is really neat!
Separately, I'm a little skeptical of the tzdb's endeavor of even thinking about pre-Unix-epoch stuff. The bug-to-utility ratio of that stuff doesn't seem to be there. `zic` is where most of the ugly gnarliness of tzdb lies, and I sometimes feel that it would have been better if `zic` weren't an artifact others could depend on.
There are plenty of people alive today with negative birth timestamps, with many services wanting to calculate the proper local day and time each year to send them annoying pseudo-personalized birthday messages.
Or, for something a bit more agreeable: genealogy (esp. the bioinformatics queries in genetic genealogy) needs a good, high-resolution timeline to normalize events onto. Actually, the non-genetic kind of geneaology, solves a lot of vagueries in lineage as constraint-based puzzles over (local!) dates, with razor-thin margins that would be messed up without correct timezone-based calendar conversion — constraints like "two people couldn't have been related as mother and child, if the mother died at least two days before the child was born."
That's a fun easter egg in the TZ database. I'd never heard of it, but how often do you need to calculate TZ data that old. Hopefully we'll be done with time zone's completely before the theory is outdated.
We'll never be done with timezones as long as we have biological ties to the Sun.
Even if you mandate that wallclocks agreed everywhere on Earth, everyone would need a replacement to know when someone is likely to respond: Is it too late to call Grandpa? and: When should I schedule this business meeting?
Nah, the weirdest time zone is Africa/Addis_Ababa, which nobody in Ethiopia follows.
Instead the locals offset the time by 6 hours. So the AM cycle starts at dawn (i.e. 6am), and the PM cycle starts at dusk (i.e. 6pm).
This is common across East Africa, including Kenya where I’m from. The night ends at 6:00AM, with 7:00AM being saa moja (first hour) of the day. Similarly, the day ends at 6:00PM (thenashara). Intuitively, this clock makes much more sense than the English clock. There’s rarely confusion between times because it’s embedded in the language.
What time is displayed on your phone when you are in Kenya? Is there a setting to make it display the commonly used time rather than the official time? I'm going to Kenya next year and I'm excited to see how my phone behaves.
Since it's pretty much on the Equator it makes a lot of sense to keep time like that -- days and nights have the same duration all year long. Such a system doesn't make sense for places that have wide variations between seasons, unless you also alter the length of the hours to match (which I think was done at some point somewhere in Europe, but I can't find any references)
Even on the equator, sunrise and sunset times will vary by +/-15 minutes, because solar days are not of equal length. But yeah, close enough for imprecise use.
This is indeed a more logical clock, as it follows the natural cycle of activity. Equally, calendars that put the end of the year at the time after harvest ("autumn"), or at the start of agricultural work ("spring") are also more logical.
Positioning the beginning of a new day at noon, and a new year t a solstice, is just a technical convenience, because these are easy to detect with very simple astronomy tools.
Only if everyone is a peasant farmer with the same crops in the same place. My activities are barely related to the height of the sun in the sky, and like the other residents of my city I don't take a ton of notice of harvest time. Bus timetables and cultural festivals are a much bigger deal (of which one in particular is indeed historically related to a harvest).
This "Day is 12 hours long" thing just doesn't work anywhere else.
I live far from the equator - "Dawn" is sometimes after breakfast, and "Dusk" can happen before I get off work.
My first thought as well as a swede. And coincidentally one of the things my old Kenyan classmate found the most strange about Sweden was the fact that the length of day was not even close to constant. That and when I explained to him that the sun being up doesn’t necessarily mean warmer weather, in the winter it’s practically takes the temperature further from zero as sun means no warming clouds…
As former Alaska resident, can confirm. December sunrises are often after 10am, and sunsets before 4pm. Vice versa in summer.
Then you get above the Arctic Circle, and there are days with neither. :D
What makes it more logical? The wheel turns all the same no matter where you mark the beginning. In the Northern hemisphere, there's actually something nice about starting the year in the dead of winter: it feels like the year is born in the spring and then dies away the following winter, not unlike a lifetime.
The whole lives of the societies which have actually invented these calendars were built around the vegetation cycle, which ruled pastures, fields, and orchards. So the yearly cycles of food availability, work, seasonal migrations, and the correlated weather pattern changes were all reasonably aligned with the start / end of the year.
Peoples as diverse as Celts, Romans, Slavs, Babylonians, Hindus, and various peoples in China all used a variety of a calendar where the yearly changes were aligned around modern October-November and modern March-April.
A calendar with the year starting in January and with astronomically (more) precise years was promulgated by Julius Caesar in -46. (I suspect the introduction of the concepts of Babylonian astrology to Rome a century before may have played a role in the desire to align the calendar to stars and not to earthly affairs.)
March should be the 1st month then I'd think. I'm pretty sure that's how the roman calendar worked. War started in spring.
If you DO start in March, your days/month fall into a neat little pattern:
Mar 31 - Aug 31 - Jan 31
Apr 30 - Sep 30 - Feb 28/29
May 31 - Oct 31
Jun 30 - Nov 30
Jul 31 - Dec 31
That highlights a few interesting cycles you can use to calculate dates from a simple count of days from the start of the year:
153 days every 5 months
61 days every 2
31 days per month
An "early reset" occurs every second month, jumping to the next 2-month cycle after the second day 30. Another occurs after every fifth month, jumping into a new 2-month cycle halfway through the last one of the 5-month. And of course, end of the year breaks the third "5-month" cycle WAY early, just before even its first 2-month is finished.
I won't try to detail the process of generating dates from this here, but I'm sure most of us here can work it out with just a little effort. Instead, here's a couple more fun facts to consider:
If you DO start the calendar from March, counting it as month 1, September (7) through December (10) map rather nicely to their own numeric positions. That seems a pretty strong hint, to me.
And I REALLY love this one:
The Gregorian cycle consists of four centuries. The first three are 36,524 days each: 100 years x 365 days + 24 days for the leap years. The hundredth year (ending in 00) is NOT considered a leap year, EXCEPT for every FOURTH hundredth. So that's 4 centuries * 36,524 days = 146,096, plus 1 more for the leap century, for 146,097.
That number is EXACTLY divisible by 7, which means the week cycle repeats WITH the Gregorian one. Good thing! Otherwise, we'd have to wait 2800 years!
Zeller's congruence for the day of the week (https://en.wikipedia.org/wiki/Zeller's_congruence) exploits this:
- months are counted as 3, 4, 5, ..., 14, with 13 and 14 being January and February of the following year
- the contribution of the month to the day of the week is floor(2.6 * (m+1)) - the 2.6 comes from the 13 "extra" days (over the approximation 1 month = 4 weeks) in every 5 months.
March was the beginning of the year not all that long ago.
That's why there frequent confusion about George Washington's birthday, along with other historical dates of that era: The New Year started in March when he was born, but changed to January during his lifetime (The British Empire switched in 1752). So being born in February, there's an ambiguity about the year, unless you specify which calendar you mean:
"George Washington was born on February 22, 1732, according to the Gregorian calendar. However, when he was born, the Julian calendar was in use, which would have placed his birth on February 11, 1731."
> it feels like the year is born in the spring
Then shouldn't the start of the year be when the year is "born"? Or alternatively, the end of the year when the year "dies"? January 1 is neither.
The year "dies" on the longest, darkest nights. (Dec 21, technically). We mourn its passing and celebrate it's life with drinks. I'm guessing there was in antiquity, a whole bunch of dreadful and exciting parties in the last 10 days around the longest nights.
It slowly grows after that and blooms later.
January 1 is so close to December 25 (when Jesus is believed to have been born) so if we wanted to count years since that -- and call it AD for "Anno Domini" (the Year of Our Lord) -- we could declare the year to begin on January 1st.
Which is exactly what we did.
January 1st became the start of the year about half a century before Jesus was born.
25 of December is close to the winter solstice (around 22nd), and I suspect it was ascribed to that day for astrological reasons; there are a few other astrological clues around that episode, most prominently, the Bethlehem Star.
> December 25 (when Jesus is believed to have been born)
I don't think anyone actually believes Jesus was born on Dec 25.
A lot of people believe a lot of things. I wonder why you don't believe that people believe this.
Now whether you yourself believe he was born then, another time or ever existed at all etc is another story.
I believe for example that everyone can believe whatever they want about those things as long as:
They leave me alone when I tell them I don't believe that and I don't want to be convinced
They don't try to kill me, enslave me, etc for being an infidel (yes that includes the Christian holy wars sort of thing but also current events)To restate more precisely: It is well-established that December 25 is a highly unlikely date for the birth of Jesus.
Children and people who have only a superficial knowledge of Christianity might very well believe otherwise. But they are poorly-informed.
Arguments against include:
a) Calendar dates are generally fuzzy from that period, particularly for events that are not formally documented. So the likelihood of anyone ever having known the correct date is very low.
b) The mythology around the birth does not match the seasonal expectations for late December (more likely springtime).
c) Dec 25 was chosen in 336 AD, by church decree. Prior to that, there was no holiday nor even a strong claim of any specific date.
d) Dec 25 was already a festival day for pagan celebrations of Saturn (Rome) and Mithra (Persia), which was likely a factor in the choice of date, to coincide with existing customs.
There are no substantial arguments in favor of December 25 being the accurate birth date of Jesus.
I don't think anyone is arguing that December 25 is the birth date of Jesus (assuming he existed), the argument is just that there are people who believe it is. You seem to think only children and people who don't know much about Christianity would believe that, but I assure you there are lots of Christian adults who don't know the history you (correctly) laid out.
The point is that the "birth date of Jesus" being set on December 25 came 350 years after January 1 was chosen to start the new year.
No the point is that my parent said:
I don't think anyone actually believes ...
When this is pointed out, he explains why it can't be Dec 25th and that's all totally fine and correct but doesn't change the fact that yes indeed there are people that believe that, as well as lots of other things that can easily be disproved. It does not matter whether you can disprove it to us and others. These people that do believe it are in fact out there.
If the year is “born in the spring” then surely you would want the year to start in the spring (if not the spring equinox, then March) and not winter?
Of course, and -- if you were Roman, for instance -- you could, for example, call the 8th month a name with "octo" (Latin for "eight") in it, or the 10th month something with "decem" (Latin for "ten").
Comment was deleted :(
Positioning of the new year at the Equinox shouldn't be any harder than doing it at the solstice (since equinoxes are halfway between the solstices), and it makes much more sense IMO. First half of the year: more day than night. Second half of the year: more night than day.
You forgot to precede your entire post with ‘Provided you live on the equator,’ which Kenya is.
If you live on the 45th parallel like I do, it isn’t logical at all since the length of a day is constantly shifting.
The problem with "more logical" here is that it's completely subjective.
The beauty of the "English clock", which isn't English at all, is that it simply defines a way to refer to the same point in time with a number (never mind that Daylight savings" nonsense) and you can refer to it whether you are a farmer, a software developer, a waiter, you live Africa or the arctic circle all the same.
didn't the julian/gregorian calendar started that way and drifted?
Of course not. Gregorian Calendar didn't drift, it just fixed drift in Julian calendar, which was like a couple of weeks by 1582. And "new year" in Julian calendar was 1st of January, same as now. It was inherited from previous Roman tradition, because Romans already had the custom to mark 1st of January as a new year, because since 153 BCE it was the date when consuls were inaugurated. So it's an entirely political thing and makes no real sense whatsoever. We are celebrating the day of Roman consulate inauguration for more than 2000 years now.
And before that they they started years from 1st of March, which is much closer to one of the Equinoxes, which is what all sane people (including french revolutionaries) consider to be the proper start of a year.
very informative, thank you
Traditional Japanese timekeeping kind of did both. The "am" and "pm" time periods started at midnight and noon, but the clocks themselves started at dawn. The hours counted down from hour 9 to hour 4 (they did not use 3-1). Each of the hours was approximately two modern hours, but their individual lengths changed every two weeks to keep the periods aligned with the sun. The twelve hours on the linear clock dials ran: 6,5,4,9,8,7,6,5,4,9,8,7 (and then a final 6 to match the first six, since it was a linear instead of circular dial).
Same with Somali. The first hour of daylight is hal saac (Hour 1)
7 AM is 1 Saac ( Hour 1)
6 PM is 12 Saac ( Hour 12)
7 PM is 1 Saac
6 AM is 12 Saac
> 7 AM is 1 Saac
> 7 PM is 1 Saac
How do you distinguish AM/PM? How does one say that something will happen 19:00 specifically, and not 07:00?
Morning and Afternoon are used for AM and PM, or if you want to be really specific you can use the name of the hour, for example 10 am is called barqo, and 18 hours is called himhimmow
https://digitalcommons.macalester.edu/cgi/viewcontent.cgi?ar...
Everyone I work with in Kenya uses standard dates and times. It’s a requirement when you work internationally.
Of course. That doesn't mean they are not familiar with the local traditional system though. They just can use both, as in many other countries such as Japan and China and in the Middle East for example.
Do they exclusively speak English as well?
Many do, yes. And I’d suspect that’s true for those the parent commenter works with in particular.
Intuitive is a synonym for "what one is used to", so I believe you when you say that according to your intuition, what you're accustomed to makes the most sense.
In a place with considerable skew in daylight hours between the summer and the winter, this would be quite unintuitive, because daylight hours would become longer (and night hours shorter) during winter and spring, and the opposite for summer and autumn.
Either that, or a fixed conventional notion of "dawn" which only corresponds to the sun rising around the Equinoxes. Either way would be unintuitive.
It's also incredibly condescending, at least the way they wrote it.
I would probably be a bit confused by the fact that 6pm is 13 hours after 5pm, but I'm assuming Swahili has better ways of communicating time
You already have to deal with the fact that 12pm is 13 hours after 11pm.
Ethiopian time keeping is peculiar all over.
https://en.wikipedia.org/wiki/Ethiopian_calendar
The Ethiopian calendar has twelve months, all thirty days long, and five or six epagomenal days, which form a thirteenth month.
That's similar to the Shire calendar system[1]. It has twelve months of 30 days, but the missing days are not in any month.
And also similar to the French Revolutionary calendar (1793 to 1805) which had twelve 30-day months and 5 or 6 jours complémentaires.
I like that Tolkien’s legendarium got the first mention here though.
The ancient Roman calendar was before that, with 10 months of 30 or 31 days and intercalated days when it's no month at all.
Sometimes priests moved these days to suit political shenanigans.
Caesar ended this madness and "rationalised" the system, coincidentally making his year-long consulship last for 446 days.
Wasn't Tolkien's LOTR partly inspired by Ethiopia?
More likely the Roman calendar.
I'm actually quite a fan of perennial calendars like that, I think the Ethiopian calendar is a much more logical system than the Gregorian system.
Almost every calendar system has a similar trick: https://en.wikipedia.org/wiki/Intercalation_(timekeeping)
The west inherits from the Romans, and Julius Caesar standardized away the Roman intercalary month by glomming it into Feburary. Before that a "priest" (the pontifex maximus) (in scare-quotes because it was a political office) would add that month on an ad-hoc basis. Not so different!
That no odder than Gregorian
It's not odd as in a more unusual system, but odd in that it is widely incompatible with the calendar of most of the world, but still official calendar. Kinda like the Kodak calendar (which was instead 13 28-day months (364 days), and iirc does the off-day adjustments over the corporate winter holiday...actually pretty reasonable)
Merry Corporate Winter Holiday!
lmao
Not reasonable at all... it's Corporate Summer Holiday around here.
You take that back!
There are good reasons for the Gregorian calendar’s oddities, though. Any simple system stops being simple when you apply it to enough different situations. I am not sure programmers would like it better if each country had a different calendar for each season. Because a day that starts at 6 and ends at 18 would make sense 2 days each years here in Europe. Not even that if you go far enough North.
Still not weirder than Lunar calendar
Why use celestial bodies at all? Let's bring the Soviet calendar back!
something something every 5 years.
That's very similar to how the romans conceived of time. Wonder if it's an old relic from when north africa was a bunch of provinces.
You'll find the ancient interpretation that the new day starts at sunset still in religions. Sabbath starts on Friday evening, Easter and Christmas day start on the eve of the day before. Possibly the Eids of Islam too, but I'm unsure.
Ethiopia is one of the ancient Christian countries, the second of officially convert and the Ethiopian Ortodox Church still seems prominent. I assume that's the reason why.
"An hour was defined as one twelfth of the daytime"
That must have been fun for the Romans here in Scotland - an hour would be roughly two and a half time as long in winter as in summer!
> That must have been fun for the Romans here in Scotland - an hour would be roughly two and a half time as long in winter as in summer!
Mechanical clocks in Japan were designed to handle those situations:
> Adapting the European clock designs to the needs of Japanese traditional timekeeping presented a challenge to Japanese clockmakers. Japanese traditional timekeeping practices required the use of unequal time units: six daytime units from local sunrise to local sunset, and six night-time units from sunset to sunrise.
* https://en.wikipedia.org/wiki/Japanese_clock#Temporal_hours
Much less of an issue without clocks.
Look where the sun is, remember where it is at sunrise/-set (much easier if you're outside every day) and then mentally divide the sky into segments and just ballpark it.
"Look where the sun is"
Well, maybe that was another problem with Scotland... ;-)
No wonder they built a few walls and retreated south....
That’s standard traditional Hebrew time still today.
Possibly simpler to explain that it is just an artifact of using sun dials for timekeeping. Sun dials technically only can tell time accurately during daylight and base-12 is an easy division of a dial (circle).
For country near equator that is not actually unreasonable system to define day cycle.
Yeah, for countries further away from the equator this would be crazy. Actually I thought Ethiopia is already far enough from the equator to have significant changes of sunrise/sunset times, but according to https://www.timeanddate.com/sun/ethiopia/addis-ababa, they only vary by ~ 40 minutes over the year, so I guess that's close enough to "constant" for most of the population...
Japan does something similar in the context of things that close after midnight: https://en.wikipedia.org/wiki/Date_and_time_notation_in_Japa...
FWIW, the English-speaking world used to switch years on March 25: https://en.wikipedia.org/wiki/Calendar_(New_Style)_Act_1750#...
Neither of these are technically things that tzdb can even talk about. They're concerned with civil time, not calendars or other "reckoning" problems.
And they live 7 years in the past.
They do. So I guess the observed timezone is UTC-61314.
Probably depends on how many of those 7 were leap years at any point in time?
Wow, this is great! This is exactly how Ive thought times should be done. Ive always called it “local sunrise time”. All the advantages of DST without the biannual spikes in traffic fatalities.
Sounds like it could be a candidate. Any system which can't be expressed in standard software is stranger than every system that can be.
Not necessarily. To be inexpressible in software, all it has to do is be unpredictable; it can still be boring.
Let me define "local snoozing time" (LST): it's set to my local standard timezone as of today, but every time I hit the snooze button on my morning alarm it shifts 9 minutes backwards (the length of the snooze). By definition, I wake up at 8am in LST, regardless of what the world is doing.
If the time shifts by more than one hour compared to the prevailing timezone, LST shifts forwards by a whole number of hours on Saturday morning, 2am LST to minimize that difference.
This timezone is "boring" but uncomputable, since it depends on unpredictable events.
But whether standard software is able to express this system is up to the software, not the system, no? Why is this way of timekeeping weird, apart from the arbitrary decision not to support it?
I would agree it's weird, but not because software doesn't support it, but because it's different from what the vast majority of the population of the world does. The fact that software doesn't support it is a downstream consequence of that.
I agree with that take. It's also quite different from saying that it's weird because software doesn't support it, which is the claim I took issue with. Maybe I should've phrased my comment differently.
The decision to not support it isn't "arbitrary" per se; it's a function of utility vs cost to implement (which a healthy dose of fudge). "Standard software" for timekeeping is far more useful precisely because it is used by far more people.
Maybe arbitrary was the wrong word. I understand that this is an implementation cost issue and I'm not saying that the decision not to pay this cost wasn't reasonable. My objection is not with tzdb, but with the characterisation of a real-life practice as weird just because software doesn't accommodate it. Shouldn't what people do be the reference for what is normal, rather than the rules encoded in software?
Individuals are full of conflicting incompatible desires and people as they group are exponentially so.
There are people who want to end any other human to ever live homeless in starvation or any kind of poverty and there are people who want to eliminate anyone they judge as threat or a nuisance while reinforcing there feeling that they dominate everything that will ever matter in the world and the rest.
Software can help all kind of purpose.
Software doesn’t accomodate it because it’s weird relative to literally the rest of the world.
Sure. But that's completely different from saying it's strange because software doesn't accommodate it.
Is it?
Yes, it is, because in your phrasing the fact that nobody else keeps time that way is the cause and lack of support in software the effect. The comment that I originally responded to is phrased as though lack of software support is the cause of weirdness.
I object to the latter since software is not the source of truth, the social practices it aims to encode are. It is perfectly reasonable to say that this particular practice is so rare that it is out of scope, but this makes tzdb a not quite correct approximation of reality, rather than reality an approximation of tzdb.
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Thats almost as confusing as the Nautical Day. Where a day on ship started at noon the "previous" day - with PM proceeding AM.
That’s also how Julian days work, they go from noon to noon: https://en.wikipedia.org/wiki/Julian_day
Interesting. I propose that the transition between AM and PM should happen right in the human-sensible middle of the day. If most people start their daily activity around 6, and retire by by 10pm, then the middle would be 14hrs.
This would also give a nice 3-part division to the day that matches their use: 1st 8 hours for the morning, next 8 hours for the afternoon, and the next 8 hours for evening/night. Currently, morning alone is 12 hours, and afternoon is like 6 (or less) and the evening takes the rest.
But I guess the current noon time is chosen for when the sun is highest in the sky, so maybe to preserve noon as the transition point, morning should start from 4:00 hrs, then the afternoon starts from 12:00 hours, and evening would start from 20:00 hours.
Ethiopian Christians have retained many Jewish customs compared to others, so you will also see them observing something like kosher diets. Although dusk is not sunset, it may be the case that they've adapted the cycle from Hebrew calendar observance.
The "Asia/Jerusalem" weirdness is because Daylight Savings Time is a big church-and-state issue. Religious people want the workday to be convenient for holidays that start at sunset.
This led to decades (up to the mid-'00s) where Daylight Savings was the result of annual negotiations between religious and secular parties. It often caused problems when the decision wasn't made until juuuust before the transition date.
There are still exceptions built in to prevent Daylight Savings from ending on Rosh HaShanah, so that's probably the future stuff.
Reading this, and considering the limited advantages of DST (especially for a country that is relatively far to the south), I wonder why they didn't decide to scrap DST completely? Maybe they will if the EU eventually manages to do it?
I would argue that DST actually makes most sense in 30-40 degrees of latitude.
With about 13 hours of sunlight in the summer, split evenly around the mid-day, it comes down to 05h30 to 18h30 under light. There are many more people who would be out there to enjoy the sunlight between 18h30 and 19h30 than there are between 05h30 and 06h30.
I really dislike this argument of "I'd rather enjoy the sun in the evening than in the morning" ignoring all of the other problems it causes.
Sunlight in the morning is useful. It's better for your sleep rhythms. It's safer for school children, etc.
And to be completely fair, I don't see that many more people "enjoying the sunlight" during the weekend when they have the entire day to do so. Like, what is the sun going down at 6 really preventing you from doing that you couldn't do otherwise?
> I really dislike this argument of "I'd rather enjoy the sun in the evening than in the morning"
> what is the sun going down at 6 really preventing you from doing
Did you take a poll, or do you just have the feeling that that is the case? Not to mention, it's a bit weaselly. It offsets the burden of defending the position to "most people".
And it doesn't even matter what "most people" think. "Most people" in this case, would be wrong. Even if it were "most people" and not "most people whose opinions you've happened to remember on the subject because they happen to align with yours".
And it's going to get darker earlier in winter. That's just what it does. People are really just lamenting the lack of daylight hours in general. Because during the winter, few places have sunlight during 6pm and 7pm even if we kept DST year round. What they say they want is sunlight between 5pm and 6pm. And after the clocks roll back, it'll start getting dark soon after 5.
And once again, I ask, for what? Having the sun rise just after 6am is better for everyone. School kids waiting for the bus are safer, kids walking to school way safer. Better driving when you're waking up. Everything is more in line with your circadian rhythms, etc.
> And it's going to get darker earlier in winter.
> School kids waiting for the bus are safer, kids walking to school way safer.
For the rest, let me give you an analogy. For several months this coming summer, I am going to give out an hour of free internet[0] each day. This won't interfere with the (paid) one that people are having otherwise. I'm not going to ask the question "would you prefer this hour to be between 05h30 and 06h30, or between 18h30 and 19h30?" but I am going to ask this question instead: What would the majority prefer, in your opinion?
[0] - any useful utility can be substituted: free hour of water, free hour of electricity, etc.
All the schools around where I live start between 7 and 8, which means kids are waiting for busses and walking between 6 and 7.
Sunrise will be at 7:12 tomorrow. Sunrise would be around 8am at the latest if we kept DST year-round.
There is less sun during the winter. That is how it works. Just in general.
Also, whenever we try "year-round DST" we go back to "spring-forward"/"fall-back" because it sucks. Everyone says they want it until they get it. Whereas Arizona has gotten rid of DST and we don't hear anything about them. They got rid of it in the 60s.
The nation should follow suit.
And all of this is outside the fact that time zones in general are more political than practical. Which is another reason people think they want year-round DST. It's because they're probably in the wrong time zone.
I don't know if you follow my argument, which is:
> DST actually makes most sense in 30-40 degrees of latitude.
Regarding your personal situation, I have no idea where you reside or what "the nation" is -- assuming US, I gather you have a "fall-back" change in three days, for a sunrise at 6:15am and up to 7am at the latest? If so, sounds like you've got it all figured out.
Summer daylight is not scarce. Between the 30th and 40th parallel is the bottom half of the United States.
DST exists so that the sun doesn't rise around 5am. And that seems to be what the argument boils down to: "I don't want it bright too early".
The sun is going down around 8pm during DST on the 30th.
If you're arguing to keep doing what we're doing, you've managed to have an even wronger opinion than getting rid of Standard Time.
> DST exists so that the sun doesn't rise around 5am.
> And that seems to be what the argument boils down to: "I don't want it bright too early".
Here is a map of the offset between solar noon and civil noon[0]. The blue places have solar noon (sun in its highest position) before their local clocks show 12h00. The red places have solar noon after their clocks show that. The white places have it about the same time.
Several observations:
1. This is without DST. With DST, blue places turn red, and red places turn even more red.
2. The map is kinda outdated, the bluest most populous country -- Turkey -- moved an hour since, so now it's white at the east and red otherwise.
3. Greenland looks the size of Africa, which is a projection issue, in fact it's much smaller, and that's even before we talk about its minuscule population.
4. There are places like Recife in Brazil, where solar noon varies between 11h03 and 11h33, but they still have more than 12 hours of sunlight most of year, and never less than 11:45, so they hardly care.
5. The vast, vast majority of the world would rather have the solar noon after 12h00 -- meaning, more light in the evening than in the early morning. Santiago de Compostella has solar noon at 13h17 at the earliest and 14h40 at the latest, "relocating" around two hours.
6. The bluest city in the USA is probably Boston, and during standard time their solar noon is 11h30-11h59. During DST, it's 12h40-12h50.
[0] http://blog.poormansmath.net/images/SolarTimeVsStandardTimeV...
> It offsets the burden of defending the position to "most people".
Decisions where the only effect is to align something arbitrary with people's preferences can only be made through appeal to the majority.
> And it doesn't even matter what "most people" think.
Yes. Yes it does.
Yeah. DST really boils down to tricking people to wake up earlier. But you can get all that sunshine by waking up earlier yourself at 5am. No need to force an awkward schedule change on everyone.
The EU likely won’t scrap it, because the CET countries want to stay in a common time zone (no new time zone borders) for economic reasons, but either the very Eastern or very Western ones in that range would object to permanent DST or permanent non-DST, because it would move them too far from the solar day either in winter or summer. It can’t be fixed without one country or another getting the short stick, which means it won’t be fixed.
If the continental US can do it (and it looks like it might soon, with California voting for it) I'm not sure I buy that argument. Heck if China can survive on one timezone...
They certainly could if they had started that way, but changing it now will disadvantage at least one of the countries (Spain for example), and those countries’ politicians don’t want to risk the ire of their voters for the greater good. And DST is regulated on the EU level, so can’t be changed by individual EU members without breaking EU law, like apparently individual US states can.
It’s status quo bias and loss aversion. Similar to how it would be better for the US to change their voting system, but it will never happen because it would disfavor one of the political parties who’d have to approve the change.
> like apparently individual US states can.
Nah, the States can’t. What we actually voted for, and I voted for this too, was that if Congress passed a law that enabled States to move to permanent DST, then the legislature is authorized to pass a law to move California to permanent DST. Congress hasn’t acted, and the main guy who was pushing for this isn’t in the legislature anymore, but basically the law did nothing except send a message from Californians saying “yeah, this sounds good, do it.” but technically it was never necessary.
States can opt-out of DST, as a few have done, but cannot choose permanent DST (assuming the relevant federal law would be deemed valid/constitutional).
https://www.kgw.com/article/news/nation-world/daylight-savin...
Correct.
Spain should take the opportunity to move to WET like Portugal
They have more economic relations with the rest of the CET countries combined, so it’s more beneficial to stay in the same time zone.
Is that not true for Portugal, or Finland in the other direction for example? I haven’t seen clear reasons for why a 1-hour offset would seriously affect economic relations particularly if it doesn’t affect when businesses are operating. Spain is already known (in stereotypes, so not sure if this holds up in reality) for later start/end times to the workday or other engagements than most western/central European countries, probably partly a figment of the time zone.
I think it's the changing times that people don't like, rather than standard time.
I'd prefer California to stay on standard time instead of staying on DST, so noon will be aligned with solar noon. (It is, right? I never actually checked.)
Well… it’s not uniform.
Take today, Nov 1st 2024, solar noon is at the following times in the State in these locations:
1pm, Crescent City: https://www.timeanddate.com/astronomy/@11788520
12:53pm, San Francisco: https://www.timeanddate.com/astronomy/usa/san-francisco
12:36pm, Los Angeles: https://www.timeanddate.com/astronomy/usa/los-angeles
12:32pm, San Diego: https://www.timeanddate.com/astronomy/usa/san-diego
It’s tempting to want to put stock in solar noon as the the thing the day should be aligned around, but honestly it’s probably overrated. Personally, I much prefer daylight savings time over standard time if I had to pick only one.
Depends how far east or west you are...
US is the same way; my hot take has always been "time to move to a -/+ 30 minute timezone"
If they didn’t have that to argue about, what else would they do with their spare time?
It's because of Passover: The Seder (main celebratory meal) lasts till midnight and later, and it's a very big deal for children.
So they don't want Daylight Savings Time to make it end even later than it already does.
It's also because of the fast day of Yom Kippur - people wanted the faster to end 1 hour earlier.
So they wanted DST to match up to those days - but that made the DST period too short, and led to the negotiations.
There is no more exceptions, IDT got extended to last Sunday of October in 2013.
According to Wikipedia: "If the end of IDT falls on Rosh Hashana, then IDT will end on the first Monday after October 1."
Reading a little further:
On July 8, 2013, the Knesset approved the bill to extend IDT even further. According to the bill, IDT will begin on the Friday before the last Sunday of March, and end on the last Sunday of October.[14]
Huzzah, at last!
> It’s not like programming languages support representing 61-second minutes anyway
This is not true. Someone already noted that Raku supports leap seconds. I think this may be partly my fault, because Perl 5's most popular datetime library, `DateTime.pm`, supports leap seconds.
It's my fault because I created `DateTime.pm` and implemented its leap seconds support. In retrospect, this was almost certainly a mistake. Almost no one cares about leap seconds. It just produces all sorts of weird confusion. Like why does adding 60 seconds produce a different result than adding 1 minute, but only rarely?
And it makes the code _way_ more complicated, especially since I wanted to validate whether setting second to 60 was valid.
This seems simple. Why not just look up the leap second table and check? Well, the `DateTime` constructor takes time components (including `second => 60`) and _any_ time zone. So we have to convert the date/time passed to the constructor to UTC in order to do that lookup. But doing that conversion ... ended up involving values that include leap seconds because of historical reasons.
It's a huge mess for very little gain.
As to Raku, I think it's stdlib datetime library borrowed from Perl 5's `DateTime.pm` quite heavily so it inherits some of the same bad design decisions.
I like that you did it and can look back with a more elegant solution.
What was the thought process originally? Were you just too focused on the problem?
I find that if I'm too close to the problem and too focused for [arbitrary timeframe], this is the type of thing that happens. The joy of fixing something before it's broken takes over.
I wrote this code in the early 2000s, so I don't remember the exact thought process. But I think my thinking was something along the lines of "this is a thing that exists, therefore I should model it 100% accurately". But I think the right way to think about it is "this is a thing that exists but most developers would be better off never thinking about, therefore I should omit it entirely".
Of course, the _real_ correct solution is to split up a date/time library into a number of closely related classes/structs, and allow users to pick the one that meets their needs. So most folks would pick the leap second-free class, but a few would use the one with leap seconds baked in.
Raku has the [Instant](https://docs.raku.org/type/Instant) class:
"An Instant is a particular moment in time measured in atomic seconds, with fractions. It is not tied to or aware of any epoch."
Earlier this year I had to write a function to find the current local time given a US address. The naive way to do so would be via a static mapping of state to time zone but there are a few edge cases that preclude doing this; in the interest of cost and speed relative to this specific application I spent a few dollars on a CSV that maps every US ZIP code to UTC offset and whether DST is followed (among other data). pytz takes IANA timezone names so I ended up having to map offset and DST info manually to specific timezones. As it turns out the US has a fair number of weird edge cases for overseas territories and military bases that necessitated the use of things like "Etc" zones [1] that have funky semantics (because of Unix for some reason if Wikipedia is to be believed).
> The naive way to do so would be via a static mapping of state to time zone but there are a few edge cases that preclude doing this
More than a few, state is really the wrong resolution here, US timezones follow counties and native reservations borders.
ZIP codes should probably be good enough but I'd be careful too. If your volume of addresses isn't too crazy, the robust way is to reverse geocode them and use a library that gets you the IANA identifier from timezone shapes.
https://github.com/RomanIakovlev/timeshape is maintained by a former coworker who could open source some of the work we did internally.
There used to be at least one airport in a tribal area in the US, that had the timezone of the reservation (not same as state) but the DST of the surrounding state (not same as reservation).
Can't remember the code for it now, had a lot of interesting timezone issues in a previous job.
My favorite is the hopi reservation, which does not observe DST and exists entirely inside of the Navajo reservation, which does observe it, and which exists entirely within Arizona, which again does not observe DST, and exists entirely within the United States which does observe DST in the general case.
I'm guessing that the airport was this one maybe? ttps://en.wikipedia.org/wiki/Window_Rock_Airport
Also IIRC (cum grano salis) the federal buildings in the Hopi reservation do observe DST and the state buildings in the Navajo reservation don't. But don't quote me on any of those actually existing.
A fun fact circa 2012 was I was writing a PHP server that needed to talk to a Windows server to schedule things. Windows server used Microsoft's own timezone system, not IANA or anything like that. I went looking for an implementation of IANA <-> MS conversion. I ended up finding all these forum posts by Windows Phone (RIP) users in Arizona who had the wrong time on their phones. So it was nice to know that 1) there was no fixing it and 2) they eat their own dogfood.
IIRC you crossed 6 time borders in 30 miles if you flew the right straight line across it.
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> state is really the wrong resolution here, US timezones follow counties
County is the smallest resolution one can reasonably use, but in terms of what timezones themselves follow, that would be metro areas. I.E. the Chicago metro area has its timezone and cities (or counties, if you will) that are part of that metro region, even when belonging to other states that largely follow a different time zone, follow the metropolis’ tz instead.
(Not arguing with you but clarifying the meaning of “follow” here.)
> US timezones follow counties and native reservations borders.
It's worse than that; Malheur County on the eastern border of Oregon is split between Pacific and Mountain time based on whether cities are more economically connected to Idaho or Nevada: https://en.wikipedia.org/wiki/Malheur_County,_Oregon#Time_zo...
As a young engineer right out of university back in 1985, one of my early tasks involved merging together a bunch of telemetry data provided on mag tapes recorded at different radar sites (in the USA). One or two of the systems time stamped their data in local time, and all the others used UTC. I remember buying one of those old Farmers' Almanacs in order to make an algorithm to account for DST. When I read the rules, I threw up my arms in despair.
The almanac gave nominal rules for the transitions. But there was a footnote explaining that these transitions had and will continue to be adjusted year to year due to Congressional intervention. I showed this to my boss and said, "If I could write an algorithm that predicted future votes of Congress, I would be a billionaire and could quit this engineering job."
I think in the end I coded the algorithm with the recent known transitions, and the nominal rules for future ones. What else could you do (this was before everyone was networked, and the code ran on standalone computers like a VAX).
I also learned that task of merging three sources of tracking data, each with its own validity and measurement degradation status, was an absolute nightmare. But still easier than predicting future actions of Congress.
This is a fantastic story, well and amusingly told.
A good approach would be to map a zip code to the named timezone (e.g. US/Eastern). Then, if you need to produce the UTC offset, apply the timezone to a date using pytz and get the offset.
The named timezone is special as it is constant. The UTC offset timezone (e.g. "-05:00") and the shorthand name (e.g. "EST") is NOT constant over time for a given location, because of daylight savings time. "US/Eastern" flips between "-05:00" and "-05:00", as well as between "EDT" and "EST".
If you ask someone what their timezone is and offer them offsets or the short names, it causes confusion for everyone.
> Earlier this year I had to write a function to find the current local time given a US address.
I also did something similar earlier this year, though I used a geolocation service to translate address to lat/long coords, and then used lat/long to translate to timezone. (With shortcuts single-timezone states)
I ended up using this python library for lat/long -> timezone converstion:
https://github.com/jannikmi/timezonefinder
Which sources its data from here, which seems like a pretty high quality source:
https://github.com/evansiroky/timezone-boundary-builder/rele...
Yeah you gotta watch out for those "Etc" identifiers, especially if you were thinking about exposing all the identifiers to your users wholesale. The file for them has this comment:
> POSIX has positive signs west of Greenwich, but many people expect positive signs east of Greenwich. For example, TZ='Etc/GMT+4' uses the abbreviation "-04" and corresponds to 4 hours behind UT (i.e. west of Greenwich) even though many people would expect it to mean 4 hours ahead of UT (i.e. east of Greenwich).
I see you too have wrestled with GreatData's time zone data being hot garbage. Been that way for decades.
The time zone in Palestine is a bit weird as well:
https://en.wikipedia.org/wiki/Time_in_the_State_of_Palestine
They have DST, but it's not on fixed dates, the government just announces each year when it's going to start and end. Sometimes with less that a week's notice, which must cause all kinds of interesting problems for people.
This is mentioned in the article.
Which leads to an interesting phenomenon where two people living in the same physical place might observe two different current times depending on how they identify ethnically and geopolitically. Israeli and Palestinian daylight savings times don't necessarily begin or end on the same day.
Not sure if true today, but used to be the case in Brazil too. Once almost missed a flight because of that.
Brazil doesn't have DST anymore. And when it had, it used to be announced with 6 months of antecedence. It also had "standard" dates that were almost always used.
If your comment was about the 2019 change that almost all computers got wrong, this one was announced with 6 months of antecedence like most others.
It's in the actual article. It's tied to Ramadan.
Without getting deep into politics I don't understand why they would prioritize spending effort on DST at all, seems like there are plenty of other concerns.
Again, without wanting to get too political, I think it's essentially bikeshedding. The Palestinian National Authority is riven with factional conflicts and has very limited state capacity. That almost inevitably leads to a lot of bickering over largely irrelevant decisions as a symbolic but hollow demonstration of political authority. The ability to make the decision takes on an importance completely out of proportion with the actual significance of the decision.
Most of the population there is interested in those dates for non-DST-related reasons. They will want to know when Ramadan begins and ends, regardless of whether it's used to determine DST.
If your life is dominated by an us vs them dynamic small demonstrations of difference become hugely important.
In a similar vein different people in Xinjiang in China observe entirely different timezones - Han Chinese observe Beijing time (because China is insane and uses one timezone despite spanning 5), while Uyghurs observe a local time 2 hours behind.
It’s a small show of resistance, which is sometimes all a people have if they have limited control of their own affairs.
You (and everyone else opining here) are missing the practical context: DST makes Ramadan easier, because the sun sets an hour earlier. Yes, you are fasting the same number of hours, but your day “starts” at a point fixed to the TZ-adjusted clock and the sooner sunset arrives, the shorter your effective day.
I don't see why announcing DST would be a big effort. And it saves on electricity costs.
Even if DST did save something (it does not), it becomes a problem when your timekeeping is done by computers. My computers know I live in Poland (Europe/Warsaw), and they know the DST rules. I can trust the time on my computers’ clock matches the official time the government recognizes.
In Palestine, this depends on my OS vendor managing to update the tz database in the short window before the official announcement and the decision coming into force. (I believe the tz database makes some assumptions based on past performance, but the government can change their mind any year.) If my OS does not update, I need to change my time zone manually to something that has the right UTC offset, and then I need to manually change back in the autumn, and I can never be 100% sure if any given computer shows the official time.
Announcing is not a big effort. Having millions of people, and thousands of companies (in the territory and outside the territory) adjusting to the announcement is a big effort. If you're going to have DST, you want it to be stable and predictable so that people can plan for it.
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I kind of thing a half hour daylight savings difference instead of an hour is a pretty low bar for the weirdest timezone. Almost any of the others are weirder: Antarctica/Troll definitely sounds weirder. The Moroccan and Gazan timezones that can't be expressed by the system as it was written because at least that means that they have some different kind of a rule, even if lunar time is well known. Same with the ones that are in Apple's naughty list because they're transitions the day before some day - again, not very weird, but at least it's weird enough to break things.
But I do agree with leap seconds: it's absolute trivia, not a useful thing for a programmer to know. Your computer smears them and you don't even know when they happened. You could completely forget them. Except that countries transitioned from ignoring leap seconds to considering them, so the switch in Australia from "GMT+x" to "UTC+x" a couple of decades ago was the transition from ignoring leap seconds to incorporating them. The fact that this is almost universally ignored is probably for the better.
> But I do agree with leap seconds: it's absolute trivia, not a useful thing for a programmer to know.
By and large, I agree with this.
But I've always found it a bit funny when a large organisation [1] says "our servers have sub-millisecond timing accuracy, thanks to GPS synchronization and these PCIe rubidium atomic clock cards we've developed" while at the same time saying [2] "we smear leapseconds over the course of a day, in practice it doesn't matter if a server's time is off by ±0.5 seconds"
[1] https://engineering.fb.com/2021/08/11/open-source/time-appli... [2] https://engineering.fb.com/2020/03/18/production-engineering...
The thing that super accurate timestamps buys you is common agreement across your infrastructure as to what the time is. This basically makes distributed systems work faster/better/whatever.
The relation between that time and what the rest of the world thinks the time is is actually less relevant.
I think the irony comes to full circle when you then use `unsmear` library to reverse the leap smearing in ntp
And then you validate against Microsoft's default `ClockSkew` of 5 minutes.
> even if lunar time is well known
The date of Ramadan is not well known because it's based on being able to see the moon from the local position on Earth. If the sky is particularly overcast for instance, then you cannot see the moon, regardless of where the moon is.
This presents problems for implementation of the calendar into the workings of a nation state. Many countries that adopt the Islamic calendar officially use an approximation, a pre-calculated date based on the moon's predicted visibility at a particular position.
The Islamic calendar is therefore not really one calendar, but two: the observational Islamic calendar and the predicted calendar, and both have a dependence on a location from which either real observations are made, or predicted observations are made.
I don't know how Morocco or Gaza do it.
> The date of Ramadan is not well known because it's based on being able to see the moon from the local position on Earth.
Note to self, look up what Islamic scholars think should be done about Ramadan on a moon base.
Not quite a moon base, but for Muslims on the ISS:
> the Malaysian government called a gathering of 150 Islamic legal scholars, scientists, and astronauts to create guidelines for Dr. Shukor. The scholars produced a fatwa, or non-binding Islamic legal opinion, intended to help future Muslim astronauts, which they translated into both Arabic and English. They wrote that in order to pray, Muslims in space should face Mecca if possible; but if not, they could face the Earth generally, or just face “wherever.” To decide when to pray and fast during Ramadan, the scholars wrote, Muslims should follow the time zone of the place they left on Earth, which in Dr. Shukor’s case was Kazakhstan. To prostrate during prayer in zero gravity, the scholars stated that the astronaut could make appropriate motions with their head, or simply imagine the common earthly motions.
I’m not an Islamic scholar (or a Muslim at all), so this is just speculation, but my guess is that if it were a permanent settlement, with people being born and living their whole lives on the moon base (so “where they left earth from” is not meaningful), they’d probably just settle on one permanent Earth time zone to follow; presumably either that of Mecca, or that of whatever country on Earth (if any) owns the base.
Prayer and pointing to Mecca seems pretty simple on the moon - but if Ramadan is based on when you can see the moon, it seems that Ramadan would start as soon as the person in charge walks by a window.
Moon-dwelling Muslims would go by the phases of Earth, if they wanted to match Earth timing but not rely on communication with Earth. The Earth as seen from the Moon exhibits the opposite phase as the reverse. Ramadan would begin when the Moon-dweller sees the Earth as being just past full. If you wanted, you could synch it with a particular timezone on Earth, by watching for when that location on Earth (Mecca or whatever) just rotated past the terminator so it experienced sundown. (Of course none of this can be directly observed if you're on the far side.) (And I get your joke about seeing the moon when you're on it; this is the practical alternative.)
Yep! I think for that case the "follow the time zone of some particular place on Earth" rule would apply.
Antarctica/Troll is not that weird. Really they use just two times: Cape Town time during short summer and Norway time otherwise. Unfortunately, Norway time happens to have DST ;-)
Leap seconds are generally trivia, but they become absolutely crucial in applications where multiple parties must be in exact agreement about chronology - the obvious example being financial transactions. A lot of markets were closed for the leap second and many banks still suspend all transactions during any change of local time to mitigate the risk of error.
Even in applications where we don't particularly care, there have been a surprisingly large number of leap second-related bugs. CGPM have decided to abolish the leap second for good reason.
https://en.wikipedia.org/wiki/Leap_second#Other_reported_sof...
And when processing satellite data.. if you're not in agreement of the time, that one second error results in a ~7km geographical error for your typical polar orbit weather satellite.
Came here looking for Troll - as far as I know it's the only one to have winter daylight savings time. Also it gets extra points for the name.
> I kind of thing a half hour daylight savings difference instead of an hour is a pretty low bar for the weirdest timezone.
Especially when, even disregarding the ones with special rules, there's a couple that are 45 minutes off.
> But I do agree with leap seconds: it's absolute trivia, not a useful thing for a programmer to know.
Maybe, all I know is that it was relevant for me during the first years in industry. If you work with timeseries which comes from source systems you don't 100% controll, like in many industrial settings, its important to know about them, and how they are handled upstream. Do the source do smearing, or does it just sync every X hours? Does it sync with NTP, which will smear (slew) the change, or have they implemented their own thing? Do they just run `ntpd -q` regularly?
But yeah, as I type it out I realize that most programmers probably don't work in that domain:-p
Excellent read around the acrobatics of timezone software. It really is quite flexible.
It leads me to wonder. If it's all just an automated and finite offset, there's no reason for daylight savings policies to hew to 60 minutes adjustments.
Couldn't a nation decide to have a continuously changing offset throughout the year? It might make their offset lookup table substantially longer, but this could 'solve' daylight savings time It'd be adjusting all the time and you wouldn't notice, just you don't notice when leap seconds occur.
Those who rely on analog clocks might no longer adjust the same direction each time!
> If it's all just an automated and finite offset, there's no reason for daylight savings policies to hew to 60 minutes adjustments.
For as long as clock sync for electronic devices has been common, I have suggested to anyone who would listen that we should adjust forward 10 minutes on the first Sunday of each month for six months, and then back 10 minutes on the first Sunday of the other six months. A ten minute change once a month is not only easier to adjust to (almost unoticeable), but if you miss it, it's not as big a deal as being off by an hour would be.
Moving up and down at a linear rate would result in a saw-tooth-like wave, but the length of days change in a sine wave. Why not have the clocks sync themselves to sunrise time based on their timezone and latitude? I don't think this would be much different, in practice, than changing times at a linear rate.
This would lead to a monumental amount of confusion.
The primary time keeping device in my house is the clock on my stove; I wear old school watches a lot; and most of my cars are old and have old clocks in them. I can't be the only one, so multiply this by at least a few million other people in America alone.
Sure, you can tell everyone they need to ditch dumb clocks and replace them with internet-enabled smart clocks. But I think that's a far more onerous undertaking than just dealing with the fact that solar time and clock time are mismatched.
More than one car per individual seems already such a waste but multiplying this at million people level, is that a real thing in USA or are you just extrapolating in your own social bubble? I mean, I must admit that I had the thought that this was just a troll that leverage on gross exaggeration of some American stereotypes, but actually I just can't decide if you are plain serious about these statements.
I have two cars (just for me, not family). Paid about $6k in total for them. You can have multiple cars without being in any particular social class
Adding to my sibling comment, time is also mostly used as a coordination system. Being offset by a few minutes would make aligning meetings with your remote coworker an even bigger nightmare than it is now.
Why don't we take it to the extreme then? Just make the time the Sun rises 6am always. And make seconds longer or shorter to adjust.
The logical conclusion of going down that route would be to dispense with the concept of time zones altogether, and just revert to using local solar time.
Which would make scheduling Zoom meetings or even just phone calls hell.
Especially when everyone's half-hour blocks are misaligned with each other's so you can't even stack meetings efficiently.
And public transport timetables, which were the original reason timezones were introduced in the first place.
This is why I think we should entirely ditch the concept of timezones. Clock time, as we use it, is largely decoupled from solar time anyway, and all attempts to reconcile the two just lead to confusion.
We already have terms a few terms to tie events to solar time, for example, a park being open from dawn to dusk. And without time zones, we might come up with a few more.
I figure everyone would just use local time locally, and unadjusted UTC for everything else.
> but this could 'solve' daylight savings time
This ignores the easiest solution to daylight savings time.
Stop doing daylight savings time.
My preferred solution would be permanent standard time rather than permanent DST, but I'll take what I can get as long as we stop changing the clocks twice a year.
Permanent standard versus permanent daylight standard is an interesting debate because some of your preference depends on which edge of the timezone you live on. It is possibly a warning that hour-wide timezones are maybe too wide and that a solution to abolishing DST may need to better account for 30-minute or 15-minute wide timezones. Right now the swing back and forth does help keep one edge or the other happier to be in the same wide timezone. Of course "switch to smaller timezones so that we can drop daylight saving time" would complicate the "simple" choice to drop DST.
India is UYC+5:30, and doesn't do daylights savings time, which is interesting for interacting with the rest of the world. Of course, China famously has one time zone despite being really wide which makes things interesting both internally and externally.
Most of the world doesn't do DST either[1], nowadays it's mostly a European/American thing.
[1] See the map at https://en.wikipedia.org/wiki/Daylight_saving_time_by_countr...
In theory, this can be expressed in tzdb. Obviously, it will cause problems.
The only really important assumption not obviously present in TZif's data format is that when you go from a local time to a UTC time, there can only be up to two possibilities. A lot of software works on that assumption, for instance java.time.LocalDateTime has a withLaterOffsetAtOverlap():
https://docs.oracle.com/javase/8/docs/api/?java/time/LocalDa...
That implicitly assumes that whenever it's ambiguous what 2:30AM means, you can only have two possible solutions (pre- and post-DST). If a timezone were ever to manipulate its offsets so that there were three or more solutions (such as if they did a "fall back" at 2:00AM and then 2:15AM or something), a lot of stuff would be unable to represent that.
Part of the issue with DST is that it makes it hard to have a consistent repeating weekly meeting time across multiple time zones that switch at different times (US vs Europe for example).
It would mean that the repeating meeting time would be at a slightly different local time every week.
> It really is quite flexible.
Other than considering current legally defined timezones as "legacy" definitions and then removing them for no reason other than to follow European fashion.
So, flexible, but managed by inflexible university types.
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Please don’t give them any ideas.
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What I like about the tz database is that's it's technically a diff of a diff. It stores the difference across history, of the difference of each timezone with UTC. Right? So it's a diff^2. But! The tz database gets updates! So those commits are diffs of diffs of diffs, or diff^3.
Can we go further? You bet! It has a changelog, and that changelog is stored in git, so commits to the tz changelog are diff^4: they are changes to the list of changes to the list of changes to the list of changes to UTC.
You forgot that UTC (or timekeeping in general) itself is a diff.
Oh that's a great point! We have achieved diff^5 at last!
Now that I think of it, we could even stretch it one more level. In practice UTC is "realized" as a "best of" diff to atomic clocks in labs around the world, which are themselves diff against a fixed time point, as you pointed out. So that realization technically changes when the official UTC bulletin[1] is published by BIPM. So diff^6!
Yes, but, it's always 5 o'clock somewhere, amiriiight??
Can we bring relativity in for another diff :)
Don’t forget using GPS to get the time and tell you if you’ve crossed time zones
So would that be diff ^ 10?
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A diff of a diff is just 2 diff. It’s not a product of diffs.
Spoilsport!
Just be rigorous with your words.
To me, one of the key framing ideas that almost all dates/times are actually a set of matching-rules that you are monitoring for. You can guess how many seconds will elapse until the match triggers, but you can't be totally sure [0] until it happens, and in some cases it will never quite happen at all. [1]
Then the second half is often to reverse your "I think it will happen X seconds from now" delta-guess into "I'm also guessing that your timezone's clocks will say Y when it happens."
Just don't forget to keep track of which timezones is controlling the event versus which timezones it is being displayed in. ____
[1] Your UTC estimate might occur plus or minus leap seconds. TAI is safer, unless somebody discovers something exciting and new that changes the behavior of cesium atoms.
[0] Such as if the time zone vanishes because the country is gone. Or perhaps the 1:30 to 2:00 thing couldn't exactly happen because the clocks went forward from 1:00 to 2:00 with a missing hour.
Another fun fact about timezones: if the government abolishes DST one year, and then moves some timezones an hour the next year, it creates a wild mess. Especially when you're building an Android app. Especially when it's the early 2010s so the timezone database is built into the system image but most devices that run your app don't receive system updates at all.
Instead of picking the timezone with the correct offset and no DST, many people would adjust the time itself so the wrong timezone and the wrong unixtime cancel each other out so the clock "looks right". Not fun when you're doing math with timestamps, some of which are local and some come from the server.
This makes me wonder: Should NTP servers broadcast the tz database...? (And should the tz database support a stable but turing-complete scripting/bytecode language?)
That sounds like the beginning of a story that ends with an RCE.
Hey, if OpenType fonts get to do it, why shouldn't timezones? :)
I worked with a group of people once who just didn't care about timezones. All (ok, most) clocks were set to local time, but with some random timezone, about half of the time it was GMT, and 2/3 of the remainder were our actual timezone, but the rest were totally random. I had to write a "figure out what the time actually is" routine in my code because it was such a pervasive problem.
I ended up doing kinda the same. Our API already had a method to retrieve the current unixtime on the server, which I used, together with the user-set timezone, to figure out the UTC offset that the user actually meant to set by adjusting their clock.
I find it slightly ironic that a blog that’s educating (and entertaining) us on time and timezones does not itself mention when its blogposts were published, at least on mobile.
This one appears to have been published in the summer of 2024.
> This one appears to have been published in the summer of 2024.
"Summer" in certain parts of the world, at least.
Sharp!
For a while (currently?) there was SEO "wisdom" going around about not putting dates on content so that search engines would treat the content as "evergreen" rather than "stale".
There's a related trend of updating the publish date so it's always today, or recent.
Thanks! The irony is not missed on me. I think I have the dates internally in the article metadata, just didn't set up my Hugo templates to display it. TODO!
Ah, so it wasn’t some SEO trick (see your sibling comment) after all :)
Thanks for the fun and informative blog post!
I figured I'd check the RSS feed to see the timestamp there, only to discover that this "blog" doesn't even have a feed!
Seems like pretty timeless content to me.
There's a couple of things that made me think the article was way older than it actually is (and made me mildly irritated that it doesn't include the publication date).
First off, the author starts off by talking about GMT and goes on to educate the reader how UTC is actually the current standard. Maybe it's just me but I thought this would be common knowledge by now, while the author frames this as some sort of a revelation.
Then there's the jab about The IERS breaking Wikipedia's css which just doesn't seem to happen on the two devices I opened it on, so I assumed that was the case prior to Wikipedia's redesign.
Minor things for sure, and the content itself is pretty timeless (heh).
Leap seconds are also set to be removed eventually. UTC will become UT1 with a fixed offset, at least until enough seconds add up for the BIPM to care about the offset and insert a leap minute or hour or something TBD.
> UTC will become UT1 with a fixed offset
I'm not sure what you mean, but this sounds wrong. The whole thing about leap second abolishment is to effectively disconnect UTC from UT1, i.e. allow DUT1 to grow unbounded and make UTC a fixed offset of TAI.
Right, swapped UT1 and TAI in my head. Oops!
While there's no explicit publication date, there are a few shell commands which strongly imply that the blogger was writing on or about "Tue Jul 30 23:52:11 UTC 2024".
I really love this way of writing. Informational with occasional bits of humor. It makes it read and ingest.
Agreed, and the humor is restrained. Often there are posts (which tend to also have an annoying amount of gifs) which just overdo it. But here it’s neatly used to lighten the writing.
Absolutely agreed, it’s a really nice conversational tone. It is technical without being dry and entertaining without watering down the information. I strive to write like this.
You should read Matt Levine's Money Stuff! I think his is the tone I roughly was going for here.
I guess I'm alone. I HATED it.
For years I've been saying that a programming course is composed of two subjects:
1. Date and Time Programming
2. Debugging
You will encounter every possible issue and common bug when doing #1, leading naturally to #2.
I think the old Riyadh timezone is the weirdest personally https://github.com/eggert/tz/blob/be62d5918223b4df209cc94163...
If you go by the wtf-ness of the comments on a tz, Asia/Riyadh has gotta be up there. But contemporarily it behaves as `<+03>-3`, which is vanilla.
agreed. From pytz's docs: "the intention was to set sunset to 0:00 local time, the start of the Islamic day. In the best case caused the DST offset to change daily and worst case caused the DST offset to change each instant depending on how you interpreted the ruling"
> It’s not like programming languages support representing 61-second minutes anyway
Raku supports leap seconds. see https://docs.raku.org/type/Instant
The article says that "Nuuk is in Greenland, and is part of the greater EU cinematic universe."
It is correct that Greenland is part of Denmark, and Denmark is a member of EU. But Greenland voted several years ago to stay out of the EU.
Which is why it's part of the greater universe, not the regular one.
Greenland is one of those spin-off movies that is part of the cinematic universe, but is generally considered to be non-canon.
Like how Spider-Man actually belongs to Sony, not Marvel, and it gets loaned back to Marvel? Or more like how Blade isn't part of the MCU, but totally belongs to Marvel?
Spider-Man belongs to Marvel, but is on conditional perpetual loan to Sony, who can optionaly loan it back to Marvel/Disney.
Sony has to release a Spider-Man movie every N months, or they lose the license, and will probably never get it again, since Marvel started making their own films and now they're part of Disney. This is why Sony keeps making reboot trilogies. Better to shovel something out than to lose the license forever. It does make a nice backstory for the Spider-Verse though.
Except Blade is part of the MCu now since Deadpool 3
But I think the analogy may be being stretched
Ahh, figures. As soon as I said it I thought it likely that Marvel had roped it in at some point.
Nothing is safe! Just wait til we get Star-Lord (Guardians of the Galaxy) accidentally facing off against some Jedi just so a writer can make some "Hans shot first" "inside" joke in some "way overshot the time travel to long ago in a galaxy far far away" plot...basically a movie to set up the joke in a trailer.
I'm just so relieved that Disney didn't buy Star Trek. Was slightly concerned by an offhand remark from the Doctor in the most recent Doctor Who series who made an off-hand comment about dropping in on the Star Trek people.
Coincidentally, Doctor Who has an unusual system where individual writers own the copyright to some of the characters they introduce, which means there's a lot of not-very-good spinoff novels (and an Australian TV show) featuring only that authors' characters.
Not sure that's the case now, but certainly was the case in the 60s and 70s with BBCs terms at the time.
Which raises the question of why none of the other heroes ever help him with all those vampires.
Also, geographically it belongs to North America. Not Europe.
In that case Greenland is accompanied by their 'sister country' The Faroe Islands, that has a similar status wrt. Denmark and EU.
> It is correct that Greenland is part of Denmark, and Denmark is a member of EU. But Greenland voted several years ago to stay out of the EU.
Greenland is still part of the EU’s overseas countries and territories. It’s not like it’s in a different universe.
EU stands for Extended Universe here, probably. ;)
So…. Antman?
Oh wow, what a coincidence, I was just looking at Lord Howe Island on a map of species conservation.
For anyone who doesn't know: Lord Howe Island is the last true paradise on Earth.
I went there on holidays a few years back based on two travel review recommendations. Both were by professional travellers that had been to pretty much everywhere, and both said it's the best place they've ever been. The reasoning was that every other tropical island has "something" wrong with it. Pushy locals trying to sell you stuff, sharks in the water, malaria, pollution, crime, poverty, or something.
Lord Howe is about as safe as it's possible to get, civilised beyond belief, pristine, unpolluted, etc...
It's one of the last places in the world with undamaged, unbleached coral reefs in protected waters. The diving there is just unbelievable, more beautiful than any Planet Earth documentary you've seen.
Birds nest on the beach, and you have to step over them gently because there's thousands of them and the juveniles can't fly yet.
I met the police officer of the island and pointedly asked him when was the last time he had to deal with crime.
"Crime... crime... let's see." he said, counting on his fingers slowly "Umm... seven years ago there was a domestic violence report because a tourist slapped his wife in an argument."
The hotel doors have no locks. There's $500 in cash in a tin next to a shack full of equipment on the beach with a "honesty system" rental price list sign next to it. The bloke selling you coke cans at the milk bar bought it with the $20 million he made in the stock market. Half the tourists go there by private plane. Ballmer's son took his super yacht there with a harem of models. And on, and on.
If you ever get the opportunity to visit: GO!
> Half the tourists go there by private plane. Ballmer's son took his super yacht there with a harem of models.
Sounds great apart from that bit.
He's not there all the time!
But did you see the stick insects?
Reminds me of when Tom Scott descended into madness at trying to account for time zones:
Somehow I end up watching this about twice a year
Me: This does not look interesting at all, but its really popular, so I'll quickly skim it. Me, 5 mins later: I can't stop reading this!
In my opinion, the best way to see it is not to pretend their are weird timezones.
It is not because most of the world do summer time and that when they do they have a 1h transitions that we should take it for granted.
This article do not mention the Chatham Standard Time Zone from Chatham Islands archipelago in NZ which is 45 minutes ahead of New Zealand Daylight Time, nor the Central Western Standard Time (Australia/Eucla). Also wikipedia mention there is a "train timezone" for the Indian Pacific train. I wonder if other trains have a dedicated timezone?
> I wonder if other trains have a dedicated timezone?
They used to, railway time is how our timezone system came to be.
> Also wikipedia mention there is a "train timezone" for the Indian Pacific train.
The only search hits I found for this claim are your comment. I find no such mention at https://en.wikipedia.org/wiki/Indian_Pacific . What are you referring to?
The great thing about Australia/Eucla is that it’s not officially gazetted, and yet there are road signs informing travellers about it. I love that people just do it and everyone goes along
I mention Asia/Kathmandu instead of Pacific/Chatham or Australia/Eucla mostly because it's not one of those "exotic birds / kangaroos outnumber humans 5:1" kinds of places.
> It is not because most of the world do summer time
Eh? Most of the world don't do summer time.
Yes for some reason I read the following sentence backwards thinking that 410 timezones were observing DST while 185 did not.
> Hmm. 410 timezones just don’t DST at all. 185 have a 3600-second, i.e. 1-hour, difference.
My point stands that there is no normality, just governments taking different decisions and being entitled to it and what the majority does is not relevant.
Is that also true by population?
Sure. The only country from the top ten by population that observes the DST is the US. From the top fifteen countries, it's US and Egypt.
I think the statement is true by any reasonable metric - population, land area, GDP size.
I'm going to steal "Greenland is part of the greater EU cinematic universe".
"Running cron jobs on an hourly basis doesn’t in practice have very weird interactions with DST"
Of course every sane person runs their default system clock on UTC and lets users pick their own local time. That way cron always does the "right thing"(TM).
That's true if you need to clean up temporary files every night or make a backup.
But what if your cronjob has an effect in the physical world, locally? E.g. open the parking gates every morning.
The world is inherently messy :-)
That sort of thing would be best handled by your own user's crontab, so would naturally inherit that user's TZ.
If you must run it as root, you can specify a CRON_TZ variable on a per-file basis, which will override the default.
> That's true if you need to clean up temporary files every night or make a backup.
Making a backup is usually reserved for the quietest hours of the morning, so that it does not compete as much for resources with the normal operation of the system; in my experience, the quietest hour is usually around 4:00 local time.
Well assuming that the gates don't move timezones. But obviously jobs that need to run for a given timezone should be configured to run in that timezone.
Unless the gates need to open at 2:30am and in the case of daylight savings time that hour is skipped.
Not if that cron file (you can have multiple cron files per user/system) is configured to run in the local timezone.
But then wouldn't the job run twice when time "falls back"?
no, it would run either twice at the "same time" as it is read out, but obviously 60 minutes apart time duration wise; but this can't be helped as this time "existed" twice in that time zone. Or conversely in spring that time wouldn't happen at all, but the cron job will still run 60 minutes apart time duration wise. But this is the downside of local time, just make sure if you want to open a door at 01:30 local time that that is what you really want, because the unintended consequences could be a bit strange.
Tangentially, Debian’s vixie-cron did / does handle DST, but it did not handle TZ changes [0], as I discovered.
[0]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1019716
A thousand years ago, every village had their own timekeeping and it worked. Our village is now earth. What if we just abandoned daylight-savings time and timezones and just went with GMT (or anything else) for everywhere on earth?
There would be cultural effects as people in California now start work at 16:00, for example...
Everyone would create local time zones and use them. It is convenient to have the clock synchronized to the local day. Using UTC optimizes for long distances when people use local clocks much more often.
How do you handle the date changing in the middle of the day? If I was on UTC, the date would change at 5pm. Is that still Wednesday or would it be Thursday?
Also, it doesn't solve the problem since still need to figure out local time when interacting long distances. If need to keep track of local times, might as well use time zones.
Finally, can solve most of the problems with time zones by including UTC time with anything long distance. Say "meeting is at 4pm, 23:00 UTC", then nobody has to worry about your local time zone.
> How do you handle the date changing in the middle of the day?
In the Jewish and Islamic calendars, the day begins/ends at sunset, and hence the date changes at that point.
Traditionally, (Western) astronomers used the astronomical day, going back to Ptolemy, in which a new day starts at noon. Part of the reason for this was that in pre-modern times it was a lot easier to precisely determine the moment of noon than the moment of midnight. Contemporary astronomy has mostly abandoned that tradition, but it still survives in the definition of Julian dates (but not Modified Julian dates which moved the day boundary to midnight)
>It is convenient to have the clock synchronized to the local day
Is it really, or are we just used to it? This seems to be busy a random reference frame.
I, for example, am an extreme night owl, and often go to sleep at 5am or later. So, to me, 12:00 is very far from the middle of the day (in fact, sometimes I'm still asleep at that time). This desync doesn't cause any problems for me.
> This desync doesn't cause any problems for me.
Are you sure you're not chronically depressed? Because our brains and bodies have this thing called a circadian rhythm, which causes all sorts of problems when disrupted. Being a night owl is no excuse, and it's often just a symptom of some underlying issue
> How do you handle the date changing in the middle of the day?
It seems like you would have to do absolutely nothing? Just like you do absolutely nothing to "handle" the hour changing throughout the day. People work overnight shifts. People schedule important events close to and on either side of midnight.
"did it happen wednesday the 23rd or wednesday the 24th?"
I wouldn't expect that confusion to be common. It's already common to say things like "I got terrible sleep on Wednesday night" even though some or all of the bad sleep might have happened after midnight and thus technically on Thursday.
Here's a good essay about that: So You Want To Abolish Time Zones [1]
That's a really good essay. My mind has been changed! Thank you!
'Global time' is a perennial HN comment on articles to do with time handling, and a truly terrible idea.
Try selling East Asia and Australia on the idea that they should wake up at 7pm, go to work on Friday, finish their workday on Saturday, and then go to bed at 11am -- for the benefit of people on the other side of the world who can't be bothered figuring out local time.[0]
Will it fix software issues around time handling? Why not, I'm sure things like having trading days on the Hang Seng stock exchange that run over overlapping two-day periods (the Nov 11-12 trading day, the Nov 12-13 trading day, ...) won't cause any unexpected issues at all. Quick, what's T+2 settlement for a trade on Nov 12?
And how would Europeans react when the global majority vote to move the suddenly-meaningful Prime Meridian to much more populous and economically important regions than London, and it's now Europe that gets to experience that kind of day, for the benefit of Tokyo and Beijing?
[0] Not to mention, 'global time' won't help with scheduling at all, since the question "what time is it there?" just gets replaced with "when do they work and sleep there?". 10am local time gives you actionable information about whether people in a given place will be awake or not, 10am 'global time' does not.
A few years ago, I bought a kit for a network-controlled self-synching clock, mostly as an excuse to practice SMD soldering. It came from a Chinese vendor, and China has only the single time zone, so the firmware was not designed with any sort of time-zone adjustment.
So I had an extremely accurate clock on my desk that was locked to Beijing time.
It was still viable, I just needed to note that it was time to get up for work when the clock said 02:00 instead of 07:00.
With regards to scheduling, we still have to negotiate when a meeting takes place-- "I may work nominally 09:00 to 17:00, but I have another appointment at 13:30", but it would eliminate the phase of trying to disambiguate "do you mean 13:30 your local time or mine?"
If you're using a shared calendar platform, specifying active hours is common anyway.
>And how would Europeans react when the global majority vote to move the suddenly-meaningful Prime Meridian to much more populous and economically important regions than London, and it's now Europe that gets to experience that kind of day, for the benefit of Tokyo and Beijing?
I'm honestly fine with it. I already often go to sleep 5am my time and wake up 13:00 (my sleep schedule is not typical), so I'm not that far from your horror scenario. But anyway, what difference does it make it people wake up at 3:00, 14:00 or 22:00? This is just a random reference frame you got used to.
Quite a few billion people are not fine with it, and I'm not seeing any serious argument designed to convince them why they should be.
No-one cares if you set your watch to UTC regardless of your latlng. Meanwhile, the rest of us will just crack on with how we've always done it.
Yeah, to be honest I don't think this idea is realistic at all. Inertia is extremely strong, and we can't get rid of much easier things (like DST, that most of the world agrees is a bad idea). I also agree that nowadays the benefits would be minor.
So I don't seriously purpose we do it, but it's fun to speculate how it could be. I think in an alternate reality where the whole world has the same hour, people would shudder at the crazy idea that every country has a different time on their clocks.
The hard part is not doing it, it's getting people to agree. I highly doubt people will agree to do that, because a large portion of people don't agree with "our village is now Earth".
In order to do computing involving time zones you also need to get an enormous number of people (particularly vendors of computer operating systems and maintainers of programming languages) to agree. But yes, this does appear to be easier than getting a few hundred political jurisdictions to agree.
Our world has gotten smaller. For people that travel often and schedule calls across time zones, time zones are a complete pain in the ass. I've advocated for getting rid of time zones for ~10 years now. It really doesn't matter if people in California start work at 16:00; the people that live in that area will get used to it. Daylight will remain the same.
UTC is problematic since it splits the day: when it's midnight in Greenwich, it's still yesterday for half the world. The Unix epoch occurred in 1969 in Hawaii.
BIT (UTC-12) is better. Only positive offsets. Everyone on the same day.
Don't you get the "it's already tomorrow for half the world" problem in place of the "it's still yesterday for half the world"?
No, not with UTC-12 (all positive offsets) or UTC+12 (all negative offsets). Any other anchor time zone creates separate days, i.e. positive and negative offsets.
What happens if a country that's currently at the new UTC-12 anchor wants to move back an hour under that system? Are they forced to "wrap around" and move to the next day instead? Or do you move the anchor itself back (to UTC-13) just to accommodate them?
Nothing to prevent sovereign countries from declaring to be on different day if they want to.
The BIT anchor would not be changed for political reasons, unless approved by residents of Baker Island.
Time zones _without_ DST would be relatively easy to deal with. The answer is not "abolish time zones", it's just "abolish DST".
I'd adjust to that better than adjusting to Daylight savings time.
Isn't that how china works? One timezone for everyone
That is good example why one timezone doesn't work. The locals in Xinjiang use a local time zone +6, instead of China time +8, because the latter is too far off the daylight hours.
My understanding is that use of Xinjiang time has dropped recently because of the crack down on Uygurs and government forcing China time.
There are various countries that optimize the number of time zones for administrative purposes, but this is much easier and sensical to implement within one country than globally.
UTC is used globally when it makes sense, e.g. for the schedules of international radio broadcasts.
This. 100%.
The most interesting timezone I ever encountered is Europe/Moscow on and around January 1, 1900. If you decide to use that date as a zero date in your code (for example, to handle the transition from two digits per year), you will be in a lot of pain: the offset was +02:30:17. Yes, with 17 seconds! Demo: https://go.dev/play/p/lq36Plr1sIL
The tzdb assumes Local Mean Time (LMT) was used all over. For example, the tzdb has Africa/Monrovia still using LMT in 1970.
> These time zones have hundreds of hard-coded transitions out into the future. I don’t understand why, it’s not like they all have lunar calendar stuff going on.
Without any additional update to the tz database, all annual transitions are assumed to continue indefinitely. So TZif version 1 would repeat transitions up to January 2038 (i.e. the end of signed 32-bit time_t), while version 2 or later would keep them for the compatibility (see the section 4 of RFC 8536) but also include the algorithmic description in the footer for later dates.
> America/Nuuk does daylight savings at -01:00 (yes, with a negative)
Somewhat related: Europe/Dublin has a negative DST offset. Irish DST runs through the European winter (i.e. the opposite of the other European timezones).
(More details here: https://github.com/golang/go/issues/56743#issuecomment-13157... )
Edit: To be clear: the quote is referring to a negative DST start, rather than a negative DST offset.
In the github repo the article links, there is a large number of comments about the Europe/Dublin time zone in the europe file, including one quote from Ulysses: https://github.com/eggert/tz/blob/7748036bace8562b9c047f368c...
I think you misread that. America/Nuuk doesn't have reverse DST (which is easily solved by just switching DST and non-DST around). It starts DST at a negative offset because the offset is defined as relative to the previous day.
Yes, this is indeed a different situation and my comment doesn't make that clear. Thank for pointing that out. I've made an edit.
Those interested in this kind of pedantry might also take care to note that it’s called “daylight saving time,” with no “s.”
It is a system of time for saving daylight.
It is not a sales event promising “savings.”
Frustrating to read an otherwise excellent and detailed article that makes this error throughout.
Both forms are widely used and accepted. Wikipedia has whole section about that:
https://en.wikipedia.org/wiki/Daylight_saving_time#Terminolo...
Thanks at least for citing a reference and not just saying “language evolves” or something.
I love time/date problems. One of the best references on the subject of calendars is "Standard C Date/Time Library: Programming the World's Calendars and Clocks" by Lance Latham. He really goes into a lot of detail on various calendaring systems, some really cooky, https://amzn.to/4hjv5L3
BTW. A long, informative post without a single mention of AI. A rare thing these days.
Clean link without affiliate code: https://www.amazon.co.uk/Standard-Date-Time-Library-Programm...
My personal favorite timezones:
There's UTC+14 in Micronesia: https://en.wikipedia.org/wiki/UTC%2B14:00
Also Antarctica/Troll: A timezone for a norwegian research station. https://en.wikipedia.org/wiki/Time_in_Norway
> Wrote a script in emacs lisp to calculate Ramadan
I found this pretty funny, but a spot on solution. The solar/calendar features of Emacs are surprisingly robust and easy to work with.
The Japanese calendar has always been the most fascinating date/time thing for me:
https://devblogs.microsoft.com/dotnet/handling-a-new-era-in-...
I always say that timezones and font rendering are the most sucking problems that developer can encounter. Both have a ton of weird quirks, both implemented differently across various target devices/OSes and require a lot of time and effort to implement reasonably right.
Despite having 4 of the 10 largest cities in the US, no Texas (or other Southern) city rates a listing in the zoneinfo file, so we're stuck having to pick Chicago, which is so far away (~1000 miles from Austin, in the middle of the state), that many people in the Southern US aren't necessarily certain what timezone Chicago is even in.
(The #10 slot varies according to source, but in general, Houston #4, San Antonio #7, Dallas #9, Austin #10. Fort Worth is nearly tied with Austin. Some sources claim Jacksonville, FL is #10, but they must be wrong...) :-)
I recall working on some calendar software and finding that at some point in the past (you have to deal with all the rules from the past) a country (Saudi Arabia?) had an offset like every day to keep solar noon in line with civil time.
At some point, adding software support for these things is just enabling bad ideas. If there wasn't support for Australia/Lord_Howe they might be annoyed into picking a simpler time zone
Does anyone understand what was meant by "This is because almost every standard (except ISO8601, whatever) is just a file, and you can read it." Initially I thought it was because the PDF of ISO-8601 is not a file commonly distributed with operating system. But that's not unique to ISO8601, you won't find IEEE 1588-2019 or NMEA 0183 v4.11 on your computer either. For ~20$ I think I can buy a PDF of the standard from ISO. Is there something special about ISO8601 that is not contained in the standard?
I believe the IEEE and others also would come under the exceptions to the "almost" - anything you'd have to make a special effort to seek out and purchase.
> Don’t let people bully you into thinking that just because something is complicated, it’s impossible. > This is because almost every standard (except ISO8601, whatever) is just a file, and you can read it.
In context, (my interpretation is that) "standard" includes things like The Time Zone Information Format [1], the GNU docs about TZ [2], etc. I think the idea is to say "the documents laying out the details of complicated things are still just documents, you can read them if you're interested and don't have to just see them as meant of domain experts. Some of them have barriers to access like the ISO documents, but even excepting those you have direct access to most everything you might want to understand, don't let the idea of standards intimidate you."
[1] https://www.rfc-editor.org/rfc/rfc8536.html [2] https://www.gnu.org/software/libc/manual/html_node/TZ-Variab...
> For ~20$ I think I can buy a PDF of the standard from ISO.
You might find most standards for ~20 USD, but ISO8601 direct from iso.org will set you back 173 CHF (~200 USD) for part 1¹, 194 CHF (~220 USD) for part 2². For $20 you get only the latest amendments from them.
Meanwhile the Estonians will gladly sell you their version of part 1 for just under 30 USD.³
¹: https://www.iso.org/standard/70907.html
Thank you. I was a little surprised by the price but I guess I naively hoped it was a change of heart from big standards.
Possibly joking about the .iso file-type for optical disc images?
Or maybe that 'most' ISO standards that are encountered by engineers are defining file-types.
I'm also a big fan of ISO-3166 though !
https://en.wikipedia.org/wiki/Sandringham_time was a crazy one
Oddly was just reading something yesterday and it mentioned that in the UK there were years during the war where we had double DST for energy saving reasons. (although we went between 1 hour and 2 hours, so it was only really a change compared to the norm)
https://www.atlasobscura.com/articles/the-extreme-daylight-s...
I don't really understand how that would save energy. Did people work 7am-3pm days or something?
The idea behind DST is that it shifts working hours into daylight hours during the darker months. This would theoretically cut down on energy use for lighting during those hours.
Of course offices, factories and even schools still use artificial lighting even during daylight hours. And now the energy use of artificial lighting is much lower than back when everything used filament.
Even ignoring the energy saving part, it sucks waking up and leaving for work or school while it is still dark.
A while ago Turkey switched to a different timezone and stopped doing DST for reasons and now everyone was waking up one hour early in winters. Considering how bad traffic is in larger cities that meant a lot of people will be waking up and going to work or school while it is still dark.
EEST (DST) is UTC+3, EET (without DST) is UTC+2. What Turkey did was abolish the DST transition but stay in permanent DST time or "summer time", which they now call TRT (which is identical to EEST).
There was a survey in parts of the EU a few years ago about abolishing DST that came out largely in favor of abolishing it. In Germany one major source of debate around the issue was that the survey referred to the timezones as "winter time" and "summer time" and predictably more people said they would prefer permanent "summer time". An equivalent survey referring to the timezones as "standard time" and "daylight savings time" likely would have had the opposite result. I could imagine that Turkey picked EEST instead of EET for similar reasons.
Having had a job for six months over the winter where I spent the majority of the 8 hour work day underground, which at times meant I'd go for days without seeing proper sunlight, I agree that this is just miserable.
I thought the main idea behind it is (or used to be) that kids can go to and return from school in daylight.
No, the main idea was to reduce coal consumption to help with the war effort during World War I (and later World War II): https://en.wikipedia.org/wiki/Daylight_saving_time#History
In Europe, in wartime. OK, good to know.
Yesterday in the UK, sunrise was about 7am and sunset was about 4:40pm. Electricity demand peaked at about 5:30pm, in the overlap between workplaces closing for the evening and people returning home and turning everything on. There's a straightforward case for either staying on BST (UTC+1) throughout the year, or (as was the case during WWII) using UTC+2 during summer and UTC+1 during winter, effectively bringing the UK in line with CET/CEST.
The key factor in the war was the blackout - street lighting was turned off for the duration and vehicle headlights were mostly covered over, to avoid providing easy targets for night bombing raids. This obviously hugely increased the hazards posed by the early sunsets under GMT.
https://www.timeanddate.com/astronomy/uk
It doesn't! That is why some countries want to leave one time for the whole year. When lots of power were used by lighting, it must have saved something...
I thing, more helpfully, that would better sync up UK time with time on much of the continent. Quite useful if you're doing a lot of things internationally.
Obligatory - David Olsen and Paul Eggert - thank you for your service. The world literally works because of your efforts and I don’t feel people really appreciate the ridiculous man made problem that you spent your labours to help resolve.
If there was a Hall of Fame of OSS contributors - you would be in it sitting on top of a mountain. The Time Zone problem is a unique problem in that its not just a problem of whats the time in this location - its what was the time in this location 20, 50, 100 years ago. The level of scholarship and historical research you put into this library is really quite unmatched. Amazing folks you two. The whole world quite literally sits on the shoulders of you two giants.
“Daylight Saving Time was first suggested as a joke by Benjamin Franklin in his whimsical essay “An Economical Project for Diminishing the Cost of Light” published in the Journal de Paris (1784-04-26). Not everyone is happy with the results.” - Paul Eggert
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A friend of mine has been visiting places with weird time related things going on, because it is interesting and takes you funny places.
He has been to Lord Howe. Now I know why. He has a user account on HN. I will ask him if he wants to make an appearance here...
Please do! Announce his arrival using his favorite time zone, and see if we can figure it out...
> Btw it’s called UTC (Universal Time Coordinated? huh?) because the same folks who publish UTC also publish UT1, which is UTC sans the leap seconds.
I’m not sure that’s right! According to legend among metrologists I’ve talked to, “UTC” was chosen as a compromise candidate: it makes sense as an acronym in neither English nor French.
So like ISO, then.
Which is not an acronym, btw, it's just styled in all caps, and is to be pronounced "iso" rather than "eye-ess-oh".
I’ve found the best way to deal with TZ conversions, is to use UTC as a common fulcrum.
I convert the target TZ to UTC, using my local utility, then use my local TZ utility to convert from UTC to local.
But I write iOS software, so I have very solid local tools at hand. It might be more problematic, on, say, a webserver.
On a related note, I wrote this utility[0], some time ago. It uses the TZ map from the TZ Boundary Builder project[1].
UTC is generally a good idea for storing, but there are still some ways to have that bite you. If a user enters a local date time for a future event in a particular time zone, converting that to UTC could result in incorrect behavior if the timezone definition changes. It depends on if the user meant that UTC time or if they meant the local time.
It can also cause trouble if you store past events but do not store the user's local offset or timezone at the time of the event. If you aggregate these events later into a dataset of "events by hour", they may be grouped wrong (from a user's perspective) if you convert them all to the user's _current_ timezone.
> if the timezone definition changes
Or if DST kicks in/out. No need to have the definitions change.
Depends on how naive the conversion is. If you consider DST while making the conversion that’s not really a problem
That's why I do it at the time the query is made. I don't ever store UTC.
You need to be careful with some circumstances. I recently had to fix up a case where someone had tried this with a recurring local date. Something needed to happen at 4am local time every day. They had converted 4am local time to UTC based on the timezone offset on the day the config was saved. This then restored incorrectly when the timezone offset changed because e.g. a DST transition.
Well, I guess I should have written in the OP, that I do both conversions at the time of the query. It's useless to try storing the UTC. It needs to be JIT.
So this is a thing: I caught the Snake emoji behaving differently in some code because it was coded one thing before #celebrity-thing, and the opposite months later.
Snake Emoji Kanye vibes are the weirdest timezone.
Wait, how is it different before/after?
> Morocco and Gaza do their daylight savings based on Ramadan.
Something about this doesn't make sense. My understanding is that Ramadan can happen at any season of the year (imagine fasting all day in Greenland during the summer!) because the Islamic calendar doesn't insert intercalary months like many other "lunar" calendars do. Given that, what is the benefit of having a daylight savings time at all if it's tied to the lunar calendar? Isn't the idea of DST tied to day length?
I wonder why the dst transition hours are encoded in local time. Wouldn't it be easier to do it in UTC? There is no need to differentiate between the same hour before and after change then.
Suppose in local time (which is, say, UTC+3) the DST transition is on something like "last Sunday of 10th month at 02:00", which might then in UTC become "last Saturday of 10th month at 23:00, except if that Saturday is the last day of the month, then the second to last Saturday". In effect, if conversion to UTC causes the transition to move to a different day, it might also be on a different week or month, causing headache.
(Or did you ask something else entirely? It wouldn't be the first time I misunderstood things about time zones.)
I bet it's North America bias—we roll our time changes across the continent one TZ at a time, at 2am local time (which also explains why the default is "/2").
Perhaps to decouple DST transition rules from other time-zone changes. So if the time-zone offset is adjusted for some other reason then the DST rule does not also need to be changed.
Correctly ingesting and visualizing data that's captured by different devices while also accounting for travel across timezones, is a real challenge. [1] is our guide how we do this for diabetes data generated by CGMs and insulin pumps.
[1] https://tidepool.stoplight.io/docs/tidepool-api/branches/mas...
A fun read! My brother actually lives on Lord Howe Island along with his wife and 2 daughters. I’m visiting them in a few weeks too actually. I will share this tidbit with them haha.
With the weirdest inhabitants like the legendary Lord Howe Island stick insect, AKA tree lobsters or more informally sausages with legs. A 20 cm long halloweenesque black beauty.
Related to the subject, can anyone recommend a book about timezones? Not a technical, programming book, but one with the history of time zones and curious use cases?
It is not exactly what you're looking for, but long ago I read this book about the invention of the naval chronometer:
https://en.m.wikipedia.org/wiki/Longitude_(book)
It's generally pretty well-regarded and closely related.
Revolution in Time is drier but still interesting and covers up past the quartz crisis starting from Babylon.
Thanks a lot!
Along with Kathmandu for weird offsets is Australian Central Western Standard Time (UTC +8:45), used in a tiny area of Australia with the largest town being Eucla (population 37). Being mainly within Western Australia (which doesn't use daylight savings) but partially within South Australia (which does use daylight savings) there has also been informal use of UTC+9:45
Historically there was also Dublin mean time (UTC -00:25.21) and Warsaw mean time (UTC+1:24)
An interesting aspect of ACWST is that it has no legal status - it's observed purely by local convention, though it's still managed to make it into tzdata.
indeed! and not only is it in tzdata, there are signs on the road telling you about it
The tz-iana mailing list is a lot of fun to subscribe to.
> With a “designator” time that doesn’t mean much
This might not 'mean much' to the computer, but it means a lot to the human. The computer uses it to communicate with the human and the humans between each other. When I arrange a meeting across timezones I will say CET 16.00 or ET3.00PM and they will understand it faster than saying how much offset we are from UCT.
Has there been any serious research regarding having a better calendar and time? We're pretty much stuck with 365.25 days per year i guess, but other than that... the one thing that's obvious is that currently it's overly complex.
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I implemented `DateTime` in Dart and Toit and wrote a blog post about the things I noticed: https://medium.com/@florian_32814/date-time-526a4f86badb
Timezones are fun...
Ever since I was assigned to work on the school website's calendar when I was in high school, I have successfully avoided any software project having to do with time and date. I feel like my quality of life has been better for it.
The best example of managing expectations of all time is in the Time Zone Database documentation:
> The tz database predicts future timestamps, and current predictions will be incorrect after future governments change the rules.
I lived in Hobart for a while and I was a firm proponent of having a Tassie south timezone that had a 2 hour winter shift to get some afternoon light. That six week pit in winter when the sun goes down at 430pm is tough.
I'd like to know the rationale behind these weird timezones, in particular non-hourly offsets to UTC. Why was it chosen that way? Why is it being upheld? It must be a big hassle.
Why not switch to a normal 60 minute offset to UTC?
tzdb often has the answer, and it's almost always because everyone used to do local solar time (i.e. on average, the sun is at the top of the sky at noon) until convenience (i.e. train and plane schedules) required an offset friendlier to mental math.
The most interesting (perhaps, the only truly interesting) thing in this writeup is his `tzdump` script. I checked his github, and it seems he didn't share it anywhere, unfortunately.
I still hope that someday the whole world will run on UTC0 and there is no more time zones madness. I know the day will likely never come but I like to keep dreaming.
Some dates will change when at relatively strange times. For some, the date change will be two hours into the workday. That seems odd. And you lose some info too: if I want a 07:30 (am) meeting, is that during the working hours of my target location? With offsets, I can see that it is 12:30pm at my target location and know that I am scheduling over lunch very likely. With no timezones, how do I know what time of day it is there? Recall some anchor time and do mental math each time? "Morning in London is 13:00, so four hours later right before lunch is 17:00, and for an LA meeting, let's see, morning there is 05:00, so 17:00 is evening time, I think
> the date change will be two hours into the workday. That seems odd
Seconds minutes and hours can change but the day cannot?
> mental math each time
Usually meetings are setup using an app and shared calendars should actually help here, a person can have meeting slots and out of office time, that should provide the same info. logistically I don't see that much of a difference from the current situation
> Seconds minutes and hours can change but the day cannot?
The calendar day being aligned to the sleep/wake cycle and changing when most of the population is either asleep or at least might not terribly care about the actual date does help quite a bit.
> Usually meetings are setup using an app and shared calendars should actually help here, a person can have meeting slots and out of office time, that should provide the same info. logistically I don't see that much of a difference from the current situation
It'd also wreck any time references in any kinds of stories that aren't consumed locally. So every time I read/watch/listen to a story that isn't set where I live, I'd first have to look up the local time to make sense of any time references.
I'd rather timezones be split based on actual logic rather than politics and eliminate things like daylight savings. It's insane to me that China has one timezone because they felt like it. People must sleep terribly in certain regions.
Yep. And the logic can be made very easy. Outside polar regions or outer space, timezone could simply be the longitude/15 degrees rounded to a constant fraction. This is not perfect as cities maybe in 2 time zones but this basically a really good approximation.
I absolutely love how this is written and hate how mouse cursor doesn't turn into pointer when hovering above links.
Hard-coded yearly transitions for a particular region, because they just have to have their own, special rules? Transitioning to DST on Sunday at -01:00 (minus one o'clock)? Or at 24:00?
Honestly, the IT world has a certain amount of influence. There comes a time where we could collectively just say "no". No, you are not that special, use any of the already incredibly flexible options that you have.
> There comes a time where we could collectively just say "no"
Well, C23 mandates a byte is 8 bits, and POSIX 2024 disallows newlines in filename, so we do exercise that right times to times.
I think you've got who's serving whom the wrong way round.
This is awesome - I have always kind of wondered how this stuff was implemented, but never looked it up.
> Yeah, this stuff is weird, but only finitely so, because ultimately a computer’s gotta implement them
Historic data can be recorded. Rules like "last Sunday in October" or "first day of Ramadan" can be implemented and handled automatically (even if the current Unix implementations don’t do non-Gregorian calendars out-of-the-box). But there can be time zones whose DST rules are "if the groundhog sees its shadow, we start DST two weeks later, otherwise, there is no DST this year". Some countries actually implement this, except the groundhog is replaced by your friendly local regime.
I’m so glad I don’t have to think about this stuff for my day job. Just miserable.
I love the zone Europe/Busingen. Büdingen has about 1500 inhabitants.
Nice morning reading
> Unless you’re doing some fairly exotic things where you’re finding yourself saying things like
>> Oh yeah the OCR on Japanese driving licenses pops out things like “平成 8”, that’s just how they sometimes say 1996 over there. That’s why we have this in the parser: eras = { "大正": 1912, "昭和": 1926, "平成": 1989 }
>> One of these days we’ll need to add "令和": 2019, but it hasn’t come up yet.
Taiwan also uses the ROC calendar[1] which is directly descended from the regnal calendars of imperial china.
But it's quaint that the Japanese name their year after one person, while us enlightened westerners simply use a calendar where it's simply the 2024th year of the, erm, hmmmph...
[1] https://en.wikipedia.org/wiki/Republic_of_China_calendar
GUWNO JEBANE
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Just wait until we decide on a time zone for the moon, or Mars.
Mars days are longer than Earth days, so a time zone alone won't do.
I think I actually heard on a podcast that some Mars rover mission team had to operate in shifts that were synchronized with Mars days.
I know this is a popular sentiment here but it bears repeating: timezones need to go away.
Time according to timezones measures the position of the sun. Except when we clearly decide with daylight savings time that we don’t care about the position of the sun, we just want it to be a certain time.
When the sun is directly over NYC it is usually 1pm or 2pm, depending on time of year, but 5pm or 6pm in London. Why? Are these events happening at different times? No, they are happening at the same time. Why do we use a different number for them?
Your “time zone” may decide that generally the workday is from 14:00 to 22:00. Why not? We already have second and third shift workers, so the idea of 9-5 is dead anyways.
When I schedule a meeting with someone in Tokyo and I am in NYC, is the meeting not happening at the same time? Wouldn’t it be easier to say “let’s do it at 13:00”? We still would need to figure out if people are awake and at work but we have to do that now while also figuring out daylight savings, so not only time but day of the year matters.
Heaven forbid you schedule a meeting or an event or a delivery or a stock trade and your time zone gets helpfully updated after you schedule the thing but before it happens. Better hope all the processes and software get that right or else!
And here is my favorite example I recently encountered: what is the speed of federal laws in the US? Say the tax brackets are rewritten for 2025, starting “January 1”. Cool, so if you work the NYE shift from 8pm to 4am in Chicago, is it the DC timezone that matters for your taxes? The local? If cannabis is legalized starting at midnight but you get arrested for possession at 11pm the day before in LA are you wrongfully detained or did you miss it by one hour?
Timezones are 19th century thinking. We can do better.
Unless you can propose a proper way to locally represent time where a person is currently present in relation to the position of the sun then no, time zones will never go away. I know time zones suck for us as programmers but it's a practical way to separate different regions that will experience different times of day differently. As long as we have clocks and times with "midnight"s and "noon"s, time zones will exist. I assume once we truly become an interplanetary species and colonise multiple planets, we will begin to use different methods of time since 24 hour/365 day clocks are going to be an Earth only thing but that's for future scientists to decide. There were proposals for daylight savings to go away but that seems to have disappeared into the ether for some reason.
Just because you personally are used to a specific type of clock doesn’t mean you can’t imagine a different kind. Submarines use 24 hour clocks and give no hecks about where the sun is.
The solution is to just use UTC. That’s it. That means in NYC you’d get to work at 13:00 and go home at 21:00, which used to be 9am-5pm. That’s it. Your whole transition has been completed. The rest is just what your calendar says. Niece’s recital on Thursday at 19:00, beers with Greg at 23:00 on Friday, etc. It really isn’t hard to imagine.
> The solution is to just use UTC. That’s it.
Okay. I work in Minneapolis and need to schedule a meeting with someone in London. How do I know what UTC time is during daylight hours for both participants? Well, we can use a formula that will tell us where the sun in the sky for a given longitude. But that's kind of a chore. So let's break ranges of longitude into zones and create a lookup table. Hang on a minute...
I've just traveled to Tokyo from Minneapolis. What time do I need to set my alarm to, to wake up an hour before most businesses open? Well, I can use trigonometry to figure out what UTC time the sun will rise at this location on Earth. But that's kind of a chore, so presumably each city will have an offset from UTC time that they all agree on to begin business hours. Hang on a minute...
>That means in NYC you’d get to work at 13:00 and go home at 21:00,
Fine.. so I'm going to have a teleconference with a company in NYC. Due to what you wrote above I now have an idea of what UTC time window to plan for - after all, I want to be able to reach them during their working hours.
Then on Friday I have to schedule a teleconf with a company in Japan. When do they work, relative to UTC? You forgot to add that, so I have to find it somewhere.
Hm, wouldn't it be nice if my computer could keep track of the working hours everywhere in the world. Let's make a database of that.. There's just one issue: How is this any better than using the timezone system we already have? Using that, I can figure out the local time in those places, and I can safely assume that they'll at least be working from around 09:00 local time. Having to instead keep track of their working hours relative to UTC doesn't seem like much of an improvement to me.
You got it exactly right up to the last sentence. Yes it is exactly the same amount of work to figure out how to make a long distance phone call or schedule a meeting.
Except for most people it is almost never a problem because most people aren’t scheduling phone calls or meetings with unfamiliar locations.
The benefit is obvious: things that happen at the same time have the same number associated with them. Just like we currently coordinate dates using a shared calendar, we coordinate times. And that has a local benefit as well. Aside from no more daylight savings time which we can achieve using other means, we also know when world events happen as they are being reported, we know when certain things take effect for countries that span multiple timezones now, we know the exact difference between any two given time points without asking “but where are they happening?”
Again, imagine that we had unified time and some country somewhere said “hey we are using the same format but doing our own variable offset from it”. That would be absolutely asinine. We are used to timezones and think they benefit us because of that familiarity. In reality we have had variable time even in the same timezones before and it was universally a bad idea that was shut down soon as people started traveling.
Oh and consider that due to cultural differences your example of scheduling meetings is already flawed: do you know if Tokyo wraps up the workday at 4pm or 6pm? Is there an hour or two hour lunch break in Barcelona? When do people actually come to work in Rome? Are banks open on Saturdays in Baghdad? Timezones do not solve these issues whatsoever so you still need to do the lookup of “when are people actually around” when scheduling a meeting outside of your culture.
1) Daylight saving time has absolutely nothing to do with this, and in any case a lot of people, me included, are of the opinion that DST is a Bad Thing and should be abolished.
2) If you want to let everybody in the world know when something specific happens (e.g. the launch of the first manned Mars mission), then you specify the time in UTC. But.. that's what we do already. Or at least those with some sense. There's still no need to force Joe Nobody to get to work at 14:00 (assuming a single world time zone) when the sun rises.. there's no advantage for people elsewhere in the world. You yourself argued that "most people aren't scheduling phone calls or meetings with unfamiliar locations". So, what's the advantage here?
3) I happen to use a calendar which is coordinated with others - it happens automatically, when they schedule something. And it has zero problem with the time - it's not just date. There's zero to gain by using UTC as localtime everywhere. That does nothing for the calendar.
4) Cultural differences in work hours: They absolutely exist. So what would having everybody use UTC help with? You still have to know those differences. It's even worse then, because if my stepson tells me "I have to work to 10AM" then I know it's late, for him. I know it instantly. If he had said "..have to work to 13 UTC" then I'm lost. I don't immediately see that he's actually working very late. I'll have to think "let's see.. he's in Tokyo, so that would be, hmm, this many hours difference from here.. is there an issue here? Oh wait, "you're working really late, will you be you okay?"
5) And that statement ".. most people aren't scheduling phone calls or meetings with unfamiliar locations". That's false. We're not in the 19th or even the 20th century anymore. The internet is a thing, and tons of people are in daily contact with people from all over the world. Just a moment ago I got a message from an airbnb guest, for example.
4) Argh, I meant 10pm or it doesn't make sense - I shouldn't try to use English time-units, I should stick to the 24-hour system I know. I always mess up that.
Traveling would be so much more disorienting. Forgetting what the local daytime range is and checking the position of the sun to guess whether you're closer to the front or back half of the day. Having to consult a table to figure out exactly how much you're going to inconvenience the person giving you a ride from the airport. Accidentally running into rush hour because you forgot that 1100 is 5:00 here. LOL.
So like when you fly from London to NYC and have no idea how long the flight actually is because it leaves at 10am and arrives at 9am? Timezones explicitly make travel harder, not easier.
Why don't people just do this then? There's no overwhelming obligation on individuals to use the local timezone.
I also think that your using the example of submarines -- notoriously an onerous lifestyle that very few are capable of living -- pretty much torpedoes your implicit suggestion that this would not be too much of a change.
The reason it is hard being on a submarine isn’t because of the clock. That’s like saying that it is hard to be a construction worker because the hard hats aren’t fashionable.
And the reason why people don’t just do that is because it is a network effect problem. We all need to buy into it. Like the metric system or driving on the same side of the road.
And people do this. Haven’t you seen people who routinely talk to people outside their timezones sign their email with their location and/or UTC work hours?
> pretty much torpedoes your implicit suggestion that this would not be too much of a change.
You did that on porpoise I hope.
OK, you're in LA. You finish work at 2300 on Monday.
You have plans to go to the theatre on Tuesday after work.
Is that 0100 on Tuesday (after finishing at 2300 on Monday) or 0100 on Wednesday (after finishing at 2300 on Tuesday)
Along the same vein… how are public holidays supposed to be handled? Do those always start and finish at midnight UTC, even if midnight UTC happens to be right during the middle of the solar day (and everybody's waking hours)? Or does every place define a specific time (aligned to solar midnight or some other suitable point during the night) for when holidays are supposed to start and end, which is basically reintroducing timezones through the back door?
> NYC you’d get to work at 13:00 and go home at 21:00
And if you plan to meet your colleagues after dinner, would you say "see you tomorrow?".
>Say the tax brackets are rewritten for 2025, starting “January 1”
U.S. income taxes are calculated on an annual basis, not hourly, so that is not an issue. (Wages are taxed according to when they are paid, which is a specific point in time, not according to when they were earned). A better example is trying to figure which calendar (tax) year an item of income or deduction belongs to. On tax professional forums, there are occasional discussions about what happens if I make a business payment online just before New Year's Day begins, but the recipient doesn't "constructively receive" it until after (or similar scenarios involving time zone differences). Do I get a deduction for the old year, but they have income in the new year? (The best answer, of course, is to not wait until a few hours before a deadline to conduct business transactions of this type, but not every type of business has that choice available).
May I recommend you read this article titled "So You Want To Abolish Time Zones"?
Look at it from the other direction for a moment: say we started with universal time. The whole world used UTC. Now try suggesting timezones. The idea would look absolutely insane. It would be a non-starter discussion.
On the other hand the transition from timezones to UTC has some challenges but the idea itself is very worth considering. What does this tell you?
Why would that look insane at all? It's like saying that letting everybody everywhere be able to say "I work from nine to five" is insane. Or that saying that the date changes to the next day when it's midnight is insane.
Because we had that. The reason GMT exists is because train stations in England all ran on different clocks. The train could leave at 11am and arrive at 10:55 at the next station because the clocks could be that far apart. And that was confusing so they said “hey you know what’s a good idea? Having a coordinated time!”
Going back to that would make things more confusing. You take it for granted that we all use the same calendar. Nobody signs your paycheck using the Chinese calendar, right? You likely agree that the US using the imperial system is silly because wouldn’t the world be in a better place if we all used metric. So why the resistance to this?
Huh? We're arguing that timezones make sense and that keeping the world in a single timezone ("UTC everywhere") would not be a good option. You seemed to argue that if timezones hadn't already been invented then the idea of a local time would be insane. That's what I was replying to.
I like the point of this article, but it takes a very long, winding, roundabout way to get there. I wish there was a better written article we could copy-paste when people make this suggestion.
I guess what I mean is, I should write one.
> Timezones are 19th century thinking. We can do better.
That's why I only use Swatch™ Internet Beats [1] for timekeeping.
Now if you'll excuse me, I have a @583.32 meeting to get to.
Meetings tend to start at most at quarter-hour intervales, or about 1/100th of a day.
If everyone used swatch times meetings would tend to start at intervals of 20, or maybe tens. Your meeting would start at @580 and last until @600 rather than 1300 to 1330 or whatever.
Nah. Any solution you come up with that accounts for how humans actually use time will just reinvent time zones. Could they be more cleanly specified than they are? Sure. But that's just an artifact of grandfathering in historical practices.
See my reply to a parallel comment.
The point is really that as long as we don't live on Discworld we have to divide the world into time zones. Either using different local time zones, or using local awake/sleep zones. Either way you have time zones.
Did you consider the aspect, that in many countries the date would change during the day?
So in UTC-5 the day would end at 19:00 solar time. „Lets meet up for dinner on Thursday“ would become completely ambiguous, depending on the time. If you move dinner on Tuesday at 18:30 (23:30 UTC) to an hour later, it would be on Friday at 0:30 UTC.
Common types calendars would become quite useless, they would need to be different for each timezone. It doesn’t make sense to split the events of one solar day into multiple day-columns in a calendar.
The vast majority of people plan their life around solar days, they usually don’t have appointments planned that span over two calendar days.
It would be an interesting experiment.
You would have to give up many concepts that have local relevance, while gaining better understanding with non-local interlocutors. I think the balance depends on how many of your daily interactions happen at local or non-local scope.
Swatch tried it in the 90s and failed. Maybe we are more globalized today...
You could also argue that different languages need to go away. Would make everything easier.
It is much harder to do. We all speak the same 24 hour clock and it is not a culturally significant thing. It would be nice if everyone could understand everyone but there is something to be lost by losing languages. There is absolutely nothing to be lost by doing away with timezones.
Of course there's something lost. If I see my colleague's local time will be 9:00PM, I know not to schedule a meeting then. It's a method for translating familiar associations of hours across space.
Also, and more importantly, "it's 5:00 somewhere!" would cease to be true.
At some point the correct solution is for engineers to collectively agree to refuse to model government-prescribed deviations from convention. Or, put more obliquely, provide more feedback to make it more obvious who is bearing the cost of the complexity of these requirements.
It's a social problem and it calls for a social solution.
I know, there's a lot of disagreement around where the point in question is, but it would serve us well if more engineers were more assertive about stating their opinion on where it is.
This sounds good until you realize that half or more of the software engineers are people working in 3rd world countries who just need a job, or they're H-1B's working in the US who can't afford to make waves.
We would need to form some kind of global union and push back together.
In the US there is a great example of a government agency that works to reduce emergent complexity in situations like this - NIST.
NIST does a lot of work behind the scenes in advanced technical fields. I wonder if it would help if there was a NIST publication enumerating common time and date keeping patterns, like we have for cryptography.
disagree - good products meet their users where they are and bury complexity under the hood. i can't imagine trying to use a calendar app (or any app really) that refuses to operate in any mode other than UTC.
OK but most people would agree that "only UTC" is not an ergonomic default. There is a balance.
Also, are the users where they are because they want to be there, or because long ago some government or religious leader forced something through and they go along with it because of some kind of inertia?
It seems like it would be so much easier to ship the tzdb algorithm as a single C library that could do arbitrary computation.
Instead, the authors prefer to use their own domain language — source files with a compiler to a binary format with a reference parser implementation. The thrust of this article is that’s mostly good enough but their domain language doesn’t include lunar information.
The downside would be size and runtime efficiency. I’m guessing tzdata is built the way it is so that it can be extremely small and efficient rather than large and, computationally speaking, comprehensive. You can run it on an Arm M0 as well as an Apple M2.
A lot of people appreciate the fact that whenever some random government decides to change of rule of their timezone (such as announcing DST changes), they only get a file update where the file is not powerful enough to be Turing complete instead of a C library update.
That’s a great point. For me though, these updates come via the same OS vendor channels that provided updated binaries too, so it’s not like I’m dodging a recompile.
Crafted by Rajat
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