Dates and times aren’t that hard—honestly!
Video is a lecture about how to think about dates and times, through the lens of a specific open source .NET library designed to aid with applying that thinking. It points out how most languages’ standard libraries really work against you, because they conflate different concepts. For example, an
Instant(a specific point in time, globally recognised) and aLocalDateTime(a date and time in a way that is irrespective of your location—for example you might want your alarm to wake you at 8:00 am on weekdays, and still do that if you move to a different time zone), aZonedDateTime(a date and time tied to a specific location—like if you want to say “the meeting starts at 10:00 am Oslo Time”), and anOffsetDateTime(a date and time tied to a specific UTC offset—which is not necessarily the same as a time zone, because “Oslo Time” is a time zone that doesn’t change, but its UTC offset might change if they go in or out of DST, or if a place decides to change, like how Samoa changed from UTC-11 to UTC+13 in 2011.These are all subtly different concepts which are useful in different cases, but most libraries force you to use a single poorly-defined “
DateTime” class. It’s easier and requires less thought, but is also much more likely to get you into trouble as a result, precisely because of that lack of thought, because it doesn’t let you make a clear distinction about what specifically it is.His library is great for this, but it’s very worth thinking about what he’s talking about even if you don’t or can’t use it. As he says in wrapping up:
You may be stuck using poor frameworks, but you don’t have to be stuck using poor concepts. You can think of the bigger concepts and represent all the bits without having to write your own framework, without having to do all kinds of stuff, just be really, really clear in all your comments and documentation.
I fucking hate timezones. Whatever it is, I’d rather read the current clock as 4 a.m. even if it’s noon than have timezones.
Only freaks have AM/PM in their time system.
24hr clock supremacy
Well you can. Just switch your clock to UTC and you’re done. You won’t even have DST to deal with.
I’m not a solipsist.
Aren’t time zones quite straightforward? You add a whole number of hours and for some a half. Compare that to a sundial on the one side and having times that don’t match your day at all on the other, I’d say it’s good
Obligatory video when it comes to time zones: https://www.youtube.com/watch?v=-5wpm-gesOY
oh you sweet summer child, what you don’t know is going to come back to haunt you forever.
Not if the place doesn’t do daylight savings time, and not all places in a timezone will do that (least in North America) so you need extra code if they do or do not. It becomes a pain after awhile when you do it in multiple projects. Technically one extra setting but it’s still a pain to make sure it’s handle properly in all cases, especially when the previous programmer decided to handle it for each case individually, but that’s a different issue.
Also when you deal with the times, say in .Net you gotta make sure it’s the proper kind of date otherwise it decides it’s a local system date and will change it to system local when run. Sure it’s all handled but there are many easy mistakes to make when working with time.
I probably didn’t even get to the real reason, I sort of picked this up on my own.
Sounds like daylight saving is the bigger issue. Maybe not bigger but when you compare cost and benefit. I think the US uses even different start and end dates than the EU and I don’t know about the rest of the world
Yeah the US differs by a couple of weeks iirc
You add a whole number of hours and for some a half
Or three quarters in a few cases.
And of course there are cases where countries spanning as many as 5 “ideal” time zones (dividing the globe into 24 equal slices) actually use a single time zone.
And then when someone tells you the meeting is at 10:00 am, you have to figure out if they mean your time zone or theirs, and if they mean theirs, you then have to convert that to yours. Oh, but your conversion was wrong because one of you went into or out of daylight saving time between the day when you did the conversion and when the meeting took place.
I agree planning around it is stupid, but I don’t see how that affects computer programs.
(let me clarify, this seems like an everyone-issue, rather than a developer-issue)
IMO the problem for developers is that they have to provide general solutions, so they have to cover each case all the time instead of just a singular case at a time.
But what is the alternative? Sure, fck daylight saving. Having the date changed at noon is fucked up, too, and that’s what happens if you agree to one global time. And having countries that are too big for a time zone is fucked up as well. Russia for example actually only spans to the Ural mountains, everything to the east are colonies. Fuck states in general #nobordersnonations
I personally would prefer if we all used UTC. My working hours would be 23:00 to 07:00. A Brits working hours would be 09:00 to 17:00, and a New Yorker would work 13:00 to 21:00.
But this does have its own drawbacks. Personally I just think those drawbacks, in the sorts of real-world time-related conversations I’ve had, are less than the drawbacks of dealing with varying time zones.
But yeah, the biggest factor is daylight saving time. Doing away with it is the number one option places that use it should take, regardless of whether one advocates for abolishing time zones or not.
Normie. Real timezone-haters use Unix epoch. /s
The drawbacks are many and the benefits are few.
Watching foreign films would be a pain, where is this in the world again, what does 19:00 mean for them? More exposition, or you just have to guess based on languag and accent.
I need this work done by our team in XYZ country, what are their working hours? (wow, look at that, still using timezones?)
When you arrive somewhere on holiday, now you have to get a sense of the time there. Or continually be thinking “what’s that in my home time?/what’s that in solar time”, which is why solar time just makes more sense.
People aren’t going to stop thinking in solar time, ever. We’re hard-wired to be awake with the sun. It doesn’t matter what the numbers are, you will associate them with the sun. The question then becomes, would we rather all use roughly the same numbers (timezones, what we currently have), or different numbers (everyone using UTC).
Using UTC solves only 1 problem, you can say verbally to someone across the world, let’s make the meeting 15:00 - but this is already easily solved by using a calendar which converts for you…
There’s a reason we have never used a single non-solar time, it’s just worse and I think there’s a reason these posts always end up on programmer focused places on the internet. Yes, I’m sure their job is annoying, and it would be easier to not have to solve time conversion problems, but the time conversion problems wouldn’t even go away if you forced everyone to use UTC. You’d just start having to do conversions to solar time, or looking up waking hours (which is just timezones)
This is a solved problem.
I think there’s a reason these posts always end up on programmer focused places on the internet. Yes, I’m sure their job is annoying, and it would be easier to not have to solve time conversion problems, but the time conversion problems wouldn’t even go away if you forced everyone to use UTC. You’d just start having to do conversions to solar time, or looking up waking hours (which is just timezones)
Which is short sighted considering it is much easier to make a standardized library for converting time zones than it is to make a standard library reflecting what different time numbers mean in different places around the world. If they somehow convinced people to make the change, they would find out pretty quickly they were better off with the devil they knew.
im a proponent of using exclusively UTC for anything pertinent to being accurate, and then using local solar time (the sun) to refer to everything else, it has the benefit of making people look outside anyway.
Aren’t time zones quite straightforward?
How very dare you!?
It’s not always whole hours
To be fair, they did say “and for some a half”.
Though that misses the Kathmandu, Eucla, and Chatham Islands, which are all :45.
you have to program a meeting that reoccurs between DST observant & non observant states in the US and australia.
Good luck.
I hate to repeat myself but DST is garbage. I never said it’s good
I don’t know what the hate is unless you are trying to store time as a String property. There a special place in hell for all developers who do this.
IMHO, all you really need to know is an Epoch time stamp and whether it’s localized to the viewer or the creator… Not that complex. The problem with time zones is that politicians keep changing them
Honestly, I’d rather give the creator of NULL a slap.
What’s wrong with NULL? How else can you differentiate between not having a value and having a blank value?
I’m probably going to get a lot of hate for this, and I do recognize there have been problems with it all over the place (my code too), but I like null. I don’t like how it fucks everything up. But from a data standpoint, how else are you going to treat uninitialized data, or data with no value? Some people might initialize an empty string, but to me that’s a valid value in some cases. Same for using -1 or zero for numbers. There are cases where those values are valid. It’s like using 1 for true, and zero for false.
Whomever came up with the null coalescing operator (??) and optional chaining (?->) are making strides with handling null more elegantly.
I’m more curious why JavaScript has both null and undefined, and of course NaN. Now THAT is fucked up. Make it make sense.
To offer a differing opinion, why is null helpful at all?
If you have data that may be empty, it’s better to explicitly represent that possibility with an
Optional<T>generic type. This makes the API more clear, and if implicit null isn’t allowed by the language, prevents someone from passing null where a value is expected.Or if it’s uninitialized, the data can be stored as
Partial<T>, where all the fields areOptional<U>. If the type system was nominal, it would ensure that the uninitialized or partially-initialized type can’t be accidentally used whereTis expected sincePartial<T>!=T. When the object is finally ready, have a function to convert it fromPartial<T>intoT.Ignoring the fact that a lot of languages, and database systems, do not support generics (but do already support null), you’ve just introduced a more complex type of null value; you’re simply slapping some lipstick on it. 😊
Type-safe lipstick :)
My suggestion has always been universal sidereal time. It is singular, doesn’t change, and carries no colonial baggage since it rotates around the whole earth. Even suitable as a home time if we become spacefaring.
doesn’t change
Citation needed.
Do you use leap seconds to stay in sync with earth’s rotation? When would they be applied? How would spacefarers be notified of these updates?
Also, what meridian do you choose for this ‘universal’ time? Is it still Greenwich? Because that’s peak colonial baggage.
peak colonial baggage
I get the thought, but wouldn’t changing it just end up performative?
I think changing the date system from AD/BC to CE/BCE is peak performative, and that’s coming from me as an atheist. We still use the same years based on the mistaken belief of when the Christ was born.
Where would we change UTC to be? Best place I could think of is where the current International date line is in the middle of the Pacific but that area is already a clusterfuck of zig zagging not that current UTC 0 is much better. And then, what do we call it? Do we keep UTC because it was a compromise between English and French speakers? Should we go with Mandarin Chinese since that is the most widely spoken language natively in the world? But there is plenty of colonialism within Chinese history of the Han people versus all other Chinese ethnicities and languages. Or English because it is the most widely spoken language when adding first and additionally spoken languages (definitely colonialism there)?
I’d sincerely love to know your thoughts on this. I’ve pondered it before and couldn’t come up with a good change besides using an artificially made language like Esperanto but that comes with a whole host of other issues.
wouldn’t changing it just end up performative
Exactly. Sidereal time does get rid of time zones and leap years, but it’s still referenced to a single physical object and relies on a arbitrary choice of start point. So it doesn’t create some perfect cosmic time standard.
The international date line doesn’t help since that’s just 180° offset from Greenwich itself.
The point of standards is that they can be followed by everyone. The AD/BC epoch is fine. The Greenwich meridian is fine. UTC is fine. Changing them would cause so much disruption that it cannot be worth it.
Daylight savings can go die in a ditch though.
“Daylight savings biting curb at 4k” as the kids would say.
Is GMT and UTC not the same? I’m happy to not have to code for timezones
You know the system before timezones was way worse, right? Every town had their own time.
That problem happened because there was no way to travel from town to town quickly so if the clocks were off nobody cared. The trains changed that.
Worst is UTC vs IAT
I used to think this way, then it was pointed out to me that, without timezones, we’d be in a situation where Saturday starts mid-workday in some places.
Fuck days! We should all just use epoch and that’s it.
Wanna meetup at 1719853000
Sure! What time?
Around 900?
Great!
And they meetup on roughly 1.7.24 17:12:00 GMT
Yeah, timezones are absolutely helpful from a logistics and coordination standpoint. Daylight savings time, though… That nonsense needs to be eliminated. So what if it will be dark well into morning wake hours in the winter, I’d take it over dealing with the time change twice a year.
Anti-DST… The almost accidental political bridge. Kinda funny actually: https://www.reuters.com/world/us/us-senate-approves-bill-that-would-make-daylight-savings-time-permanent-2023-2022-03-15/
Look at the names of the quotes. Both sides are commenting on how dumb it is.
Then the House got involved.
that-would-make-daylight-savings-time-permanent
fwiw this is by some metrics even worse than switching back and forth
There are good sides to DST, such as coming home “earlier” (by the sun clock but not by the social clock) from school or work and therefore having more hours of daylight during the free time after work. These positive effects may go beyond subjective feelings. A study has shown for example that activity increases with longer evening daylight (Goodman et al., 2014) – albeit with small biological effect sizes (≈6% difference in the daily activity between the Standard Time of the year and DST, adjusted for photoperiod). Interestingly these results of the above study were culture-specific: a significant increase was mainly observed in Europe and to some extent in Australia, while no significant effects or even slightly negative effects were seen in the United States and Brazil.
Fucking duh. This is the sticking point for me, and I am disappointed that the article doesn’t mention the effect of latitude here. Very easy for muricans to say “DST is not useful” when these fuckers never get pitch-black night before 6pm or full daylight before 6am ST.
Brussels is on the same latitude as Calgary. ST robs every office worker of one hour of useful daylight. That’s it. That’s the whole argument for permanent DST. Businesses will not change their opening hours, so permanent ST means a net loss of one active hour in the day for every office worker. Permanent DST in Europe means someone working 9-6 would not have to drive home at night for 4 months of the year and could maybe even take the dog for a walk in the evening sun.
You realize there are places without it, and they’re fine, correct?
Not sure what you mean. My position is that daylight saving time should be abolished entirely. You linked an article about a push to move permanently on to daylight saving. I pointed out how that is actually a bad idea.
I just linked it to show the rare piece of bipartisanship. I agree DLST should be done away with. As to which schedule to keep, I find it to be 6 of one and half dozen of another. The difference is just another nit pick someone will find excuses to argue over.
The difference is just another nit pick someone will find excuses to argue over
No, it isn’t. The scientific research actually suggests that keeping DST is worse than switching back and forth. I have to admit I find that confusing, since a lot of the specific studies I’ve looked at concentrate on the effects caused by the switchover itself, but the meta-analysis doesn’t mince words:
In summary, the scientific literature strongly argues against the switching between DST and Standard Time and even more so against adopting DST permanently.
I have never really understood why people care so much about the change.
You will just wake up one hour later or earlier twice a year, so what? I do that multiple times a week, twice per year isn’t too bad.
I’d say the people in that 24% have a quite valid reason to care.
You obviously don’t suffer from a sensitive circadian rhythm. To that I’d say, lucky you. But there are plenty of people who do suffer. And by the time they finally get used to the time change, it’s time to change again. It’s vicious and disruptive; to more than just scheduling. It has a direct (negative) impact on physical and mental health.
Fair enough. Personally I and many others in northern Europe (and other places far from the equator) feel depressed in winter due to the highly reduced sunlight so removing DST isn’t just as obvious as “people will feel better”, because DST at least in theory helps with that.
Yeah, Seasonal Affective Disorder is a recognised medical condition and its symptoms get worse the further from the equator you live. Don’t know why folks are downvoting you for having it.
timezones are absolutely helpful from a logistics and coordination standpoint
They’re a downside from a coordination standpoint. If everyone was on UTC, you could say “the meeting is at 04:00” and everyone, anywhere in the world, will know when the meeting is. In the real world, you have to say “the meeting is at 2pm AEST” and then someone in AEDT will have to think “oh, that’s 3pm for me”, and someone in American EST will have to convert to UTC and then convert to their time. It’s a huge pain.
So what if it will be dark well into morning wake hours in the winter
That’s not something that DST does. It would be something that switching to year-round DST would do, but permanent standard time doesn’t change winter hours at all. It can mean you might have dark mornings (especially early and late summer—after the switch to DST and before the switch back to standard time), depending on how far west you are in your time zone and how far away from the equator you are. That’s the main thing DST does: swap bright mornings for bright afternoons in summer. Which is kinda silly considering it’s done at the time of year when afternoons are already bright for the longest. It’s also very harmful to public health.
But… We have UTC already, so calculating the difference is a non-issue. If you got rid of timezones, you’d still end up creating it in all but name since the vast majority of business will be occurring during daytime hours around the world. For example, an office in Tokyo sending emails to their NYC office at 0800 UTC (currently 0400 EDT in NYC) wouldn’t end up getting answered for at least 3-4 hours when those employees started logging in. In other words, people would still be doing calculations in their heads to know when business hours are in that region, essentially recreating timezones.
As for your second paragraph, I agree, and I did have it backwards, thanks for the correction. In the summertime where I live, the sun has risen by roughly 0530 and sets around 2100. In the wintertime, the sun is rising around 0700-0730 and setting around 1630-1700 at its shortest daylight hours. Like you said, staying at standard would mean in the summertime we’d have brighter mornings, but curtains and shutters exist for a reason. Personally, I think having it still be bright out at 2030 is kind of annoying.
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For some offices, tech like Teams/Outlook would certainly help, sure. But the majority of offices aren’t using that. But even still, people would do it regardless. Say you’re going on vacation and want to know when daylight hours are, you’d still be doing the same thing. Timezones may be annoying, but they ultimately make sense. We have a universal time for the planet powering the system, there’s really no reason to change it, in my opinion.
Eliminating time zones doesn’t make scheduling meetings easier it just changes the language. Instead of figuring out what time it is elsewhere you have to remember what normal working hours are, Europe, US, and Japan aren’t all going to be available 9-5 UTC. It’s just as easy to suggest a meeting at functionally midnight without time zones.
Yeah you’re absolutely right that it does create a tradeoff. My experience has just been that I’d usually consider it a worthwhile tradeoff. In general, the number of people who have to deal with setting meetings is lower than the number of people who attend meetings, especially when you take into account multinational companies.
And when you’re attending a meeting, you only care about knowing what time it has been scheduled for already. It’s in scheduling that you have to work out when is going to be best for your audience, and I’m of the opinion that the distinction between “what time is this in my time zone and their time zone?” and “where does this time sit in relation to their working day?” is net neutral. With one aspect being a strict positive and the other being a net neutral (in my opinion), I think it still wins out and becomes worthwhile.
I’d argue not every job will always be 9-5, so you still get people having to explain working hours with non-UTC timezones anyway, whereas all timezone conversions are eliminated if everyone uses UTC.
Assuming you used UTC as the shared time zone, 00:00 on Saturday would start at what is today 4pm in US Pacific Standard Time. So you’d finish work at 01:00 Saturday.
On the other hand, you wouldn’t resume work until 17:00 on Monday.
So you’re not losing any weekend time.
People who work night shifts already experience this. It’s not as disorienting as it seems.
It could have been worse. The romans had the day divided into 24 hours, like we do, but the hours varied in length so that from sunrise to sunset, you would always have 12 hours.
Imagine if that was the agreed upon time system, and we had to program that into computers.
It’s called temporal hour. Many cultures around the world had such a time system. Like in Japan they made clocks and watches that could tell temporal hours called wadokei.
Conversion for metric system is a pita also
Which conversions? Most metric conversions are drastically simpler than their imperial counterparts.
Nah. Metric should have just been base twelve.
Timezones are fine to program around.
DST is a bit of a pickle to plan around, but can be done just fine by a computer program.Historical dates; considering leap years, skipped leap years, and times when leap years weren’t a thing or when humanity just decided we skip a bunch of years; are the bane of all that is good.
Proleptic Gregorian Calendar enjoyers
I hear timezone names can also be a slight issue at times, some Australians call the eastern time zone EST. Leap years aren’t so bad at times either though. Kind of agree with the rest of it, much of the complexity is from historical dates.
We call eastern coast time AEST
I know most call it AEST, but there are some who call it EST.
IMO, the biggest problem with timezones is that the people who initially created them were fairly short sighted.
That and there have been way too many changes to who lives in what timezone. The one that boggles my mind is that apparently there’s a country in two timezones, not like, split down the middle or anything, but two active timezones across the entire country depending on which culture you’re a part of, or something. It’s wild.
I still don’t know if there’s any difference between GMT and UTC. I couldn’t find one. They both have the same time, same offset (+0), and represent the same time zone area.
I use UTC because I’m in tech, and I can’t stand time formats, so I exclusively use ISO 8601, with a 24 hour clock. Usually in my local time zone, via UTC. We have DST here which I’m not a fan of, but I have to abide by because everyone else does.
My biggest issues with time and timezones is that everyone uses different standards. It drives me nuts when software doesn’t let me set the standard for how the time and date is displayed, and doesn’t follow the system settings. It’s more common in web apps, but it happens a lot. I put in a lot of effort to try to get everything displaying in a standard format then some crudely written website is just mm/dd/yy with 12h clock and no timezone info, and there’s nothing you can do about it.
I know people who actively fight me on ISO 8601. They don’t like the way it sorts their files/folders, reliant on whatever behavior the operating system does. Whenever data recovery happens or their files are moved, all the change times are blown out the window and the sorting they expect is blown away.
I’m not yet using a 24-hour clock. But it has me thinking. That’s not such a bad transition for 24-hour local time into UTC. Or just using both. At some point the inconvenience of the local will become vestigial and UTC is what remains.
I use 24h clocks and ISO 8601 dates almost always
Honestly, I’m better at organizing code than I am my actual life
UTC exists as a historical compromise because the British felt that GMT was the bees knees and the French felt differently. The letter order is most definitely a compromise between French and English word order. You can call it Universal Time Coordinaire.
Historically, GMT became the international time reference point because the Greenwich observatory used to be the leader in the field of accurately measuring time. It probably helped that the British navy had been dominant earlier and lots of countries around the world and across time zones had been colonised by the British.
UTC is an international standard for measuring time, based on both satellite data about the position and orientation of the earth and atomic clocks, whereas GMT is a time zone. Nowadays, GMT is based on UTC not independent telescopic observation.
What’s the difference? You can think of a time zone as an offset from UTC, in the same sense that a 24h clock time is an offset from midnight. GMT = UTC+0.
Technically, UTC isn’t a valid time zone any more than “midnight” is a valid 24h clock time. UTC+0 is a time zone and UTC isn’t in a similar sense that 00:00 is a time in 24hr clock and “midnight” isn’t.
Of course, and perfectly naturally, I can use midnight and 00:00 interchangeably and everyone will understand, and I can use UTC and UTC+0 interchangeably and few people care, but GMT = UTC+0 feels like the +0 is doing nothing to most eyes.
Fun fact: satellite data is very accurate and can track the UTC meridian independently from the tectonic plate on which the Greenwich observatory stands. The UTC meridian will drift slowly across England as the plates shift. Also, the place in the stars that Greenwich was measuring was of by a bit, because they couldn’t have accounted for the effect of the terrain on the gravitational field, so the UTC meridian was placed several tens of metres (over 200’) away from the Greenwich prime meridian. I suspect that there was a lot more international politics than measurement in that decision, and also in making the technical distinction between UTC and GMT, but I’m British, so you should take that with a pinch of salt.
That’s quite the lesson you just laid down.
It’s actually made things a lot more clear for me. To put it as tersely as I can, UTC is the international time, GMT is a timezone, which also happens to be UTC+0.
So GMT is a place/zone/region of earth, and UTC is a time coordination, with no physical location (beyond the prime meridian, which is where it is tracking the time of).
Awesome.
I would truthfully and happily go back in time and tell people not to waste with the fucked up bullshit technology of the past. I mean Angular 1, what the hell was that? Twitter integration? Fuck you 2010. Zend Framework? You should be hanged. HANGED.
