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It’s not just time zones and leap seconds. SI seconds on Earth are slower because of relativity, so there are time standards for space stuff (TCB, TGC) that use faster SI seconds than UTC/Unix time. T2 - T1 = [God doesn’t know and the Devil isn’t telling.]
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We use datediff in sql and let God handle the rest.
“Oh but they’re in different time zones” “Oh did you account for if one is in day light savings and other isn’t” “Aren’t some of these dates stored in UTC and some local?”
Are all problems I do not care about.
This is why we should just move to a universal time zone and stop with the day light savings.
We have that, it’s called Unix time, and the only thing it doesn’t account for is time dilation due to relativity.
If your system hasn’t been upgraded to 64-bit types by 2038, you’d deserve your overflow bug
Let’s just nake it 128-Bit so it’s not our problem anymore.
Hell, let’s make it 256-Bit because it sounds like AES25664 bits is already enough not to overflow for 292 billion years. That’s 21 times longer than the estimated age of the universe.
If you want one-second resolution, sure. If you want nanoseconds a 64-bit signed integer only gets you 292 years. With 128-bit integers you can get a range of over 5 billion years at zeptosecond (10^-21 second) resolution, which should be good enough for anyone. Because who doesn’t need to precisely distinguish times one zeptosecond apart five billion years from now‽
If you run a realistic physical simulation of a star, and you include every subatomic particle in it, you’re going to have to use very small time increments. Computers can’t handle anywhere near that many particles yet, but mark my words, physicists of the future are going want to run this simulation as soon as we have the computer to do it. Also, the simulation should predict events billions of years in the future, so you may need to build a new time tracking system to handle that.
With a 128 bit integer you can represent 340 undecillion (or sextillion if you use the long scale notation) seconds, which is equivalent to 10 nonillion (or quintillion, long scale) years. The universe will long have have stopped being able to support life by then because stars stopped forming (enough time would have passed it could have happened a hundred quadrillion (a hundred thousand billion, long form) times over assuming we start counting from the birth of the universe).
Cries in vintage computer collection tears.
You are a monster phoneymouse
I thought that’s what datetime was based off of, tbh.
I know, but it’s not standard anywhere in the world.
Give it a few more decades
Swatch’s Internet Beats are making more and sense every time Daylight Savings forces a timezones change. Why are we still using base 12 for time anyway?
From the wikipedia:
TCB ticks faster than clocks on the surface of the Earth by 1.550505 × 10−8 (about 490 milliseconds per year)
It’s amazing that this level of detail is relevant to anything.
Without considering this, most people wouldn’t be able to drive anywhere they haven’t been before anymore.
“Wouldn’t be able to” is a bit of a stretch, since Thomas Maps existed long before GPS. But it wouldn’t be so easy as it is now.
Most people couldn’t use a Thomas guide in the mid 90s either.
Thank you, but I gave up halfway through the list.
I got to “The day before Saturday is always Friday” and I was like waaaa?
I thought it is about when Julian calendar was dropped in favour of Gregorian, but that’s not it:
Thursday 4 October 1582 was followed by Friday 15 October 1582
Also some of the islands around the International Date Line did switch their stance on which side of the Date Line they are. So… they might have had a day twice or lost a whole day in the process. And maybe, they didn’t change sides only once…
E.g. see here https://youtu.be/cpKuBlvef6A
Epoch is your friend, or use UTC. At least that’s my layman reasoning. I have no challenges working with DateTime except when I don’t know the underlying conditions applied from the source code.
I really wish that list would include some explanations about why each line is a falsehood, and what’s actually true. Particularly the line:
The software will never run on a space ship that is orbiting a black hole.
If the author has proof that some software will run on a space ship that is orbiting a black hole, I’d be really interested in seeing it.
Technically isn’t the Earth itself a sort of space ship which is orbiting (…a star which is orbiting…) the black hole at the center of the Milky Way galaxy? Not really close enough for time dilation to be a factor, but still.
All links to the original article are dead and even archive.org doesn’t have a capture either. I guess the argument is along the lines of “it might not be relevant, when you’re scripting away some tasks for your small personal projects, but when you’re working on a widely used library or tool - one day, it might end up on a space vessel to explore whatever.”
E.g. my personal backup script? Unlikely. The Linux kernel? Somewhat plausible.
Well in a very strict sense one can’t really say “never” (unless you can see into the Future), but it’s probably safe to go along with “It’s highly unlikelly and if it does happen I’ll fix it or will be long dead so won’t care”.
Does anyone know what is untrue about “Unix time is the number of seconds since Jan 1st 1970.”?
When a leap second happens, unix time decreases by one second. See the section about leap seconds here: https://en.m.wikipedia.org/wiki/Unix_time
As a side effect, this means some unix timestamps are ambiguous, because the timestamps at the beginning and the end of a leap second are the same.
It might be more accurate to say that Unix time is the number of days since Jan 1st, 1970, scaled by 24×60×60. Though it gets a bit odd around the actual leap second since they aren’t spread over the whole day. (In some ways that would be a more reasonable way to handle it; rather than repeating a second at midnight, just make all the seconds slightly longer that day.)
This one is good (or evil, depends on how you see it):
Human-readable dates can be specified in universally understood formats such as 05/07/11.
That one’s really good.
Which one is it?
- July 5th 2011
- May 7th 2011
- July 11th 2005
- November 7th 2005
And is it 2011/2005 or rather 1911/1905, 1811/1805,…?
This post made my head hurt
Ah I’ve gotten to the point where I have to define what “frame” and epoch each time base is in before I’ll touch the representation of time( Unix,Gregorian, etc) .To be honest I’m probably just scratching the surface of time problem.
Hell probably the reason we haven’t seen time travellers is we suck at tracking time and you probably need to accurately know your time and place to a very good precision to travel to a given point and we can’t say where and when that is with enough accuracy to facilitate where to land. And people don’t want to land in the earth’s surface or 10000 km away from a stable orbit. Maybe some writer can build that out for a time travel book or to discount it for some reason lol
I recall a short story like that where someone died because they time traveled, but didn’t account for position.
Highly recommended
Holy crap I wasn’t ready for that. Great rec tho
Really good, thanks
SPOILER
I want little Emily to change her future. A sequel is needed!
–
(Thanks for sharing, was a good watch.)
There are… 2 sequels
Good luck finding them though!
There’s link in the description, it’s just that those are a bit costy ($8 just to watch on Vimeo)
LOL whenever I have to work with DateTime systems that try to account for every possibility (and fail trying) I am reminded that in some disciplines, it’s acceptable to simplify drastically in order to do ‘close enough’ work.
I mean, if spherical cows are a thing because that makes the math of theoretical physics doable, why not relativity-free date-time measures that are willing to ignore exotic edge cases like non-spherical livestock?
Not even going to general relativity, as this comics suggests to experience time slowing down due to gravity, the events are not just at time, but also at particular location in space relative particular inertial system. Not specifying it, and not specifying the inertial system for which the final answer is needed makes it impossible to calculate even in special relativity, without effects of gravity.
Here’s the shortlist of horrors I’ve had to deal with in my career:
- Mixed US/ROW short date formats - DD/MM/YY, MM/DD/YY
- mixed timezones in the same column
- the wrong timezone (marked as PDT but actually UTC, or sometimes the other way around)
- clock drift
- timezones again…because timezones suck
- historical timezones
- NTP configurations
Things I’ve read about but haven’t needed to deal with personally:
- leap seconds
- clock slew vs skip
- hardware clocks
- PTP
The one thing I really don’t care about is relativity
it’s all relative anyway
t2 - t1 = what even is time anyway???
We can divide by t and then we get 2-1=1. Simples!
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Relevant Tom Scott video the answer depends on location, times, country, religion, and a bunch of other factors.
Scrolled trough here just to search for this comment 😂
I wonder what fraction of xkcd readers have already seen this video… I imagine it is quite high. I know I’ve watched it multiple times. It’s a good one.
That’s me in the bottom right corner over there.
Is it you in the bottom right spotlight over there?
C++ user with operator overloading: “T2 minus T1.”
Let someone else implement the class. There’s probably a library for it.
I just spent two days debugging a reporting endpoint that takes in two MM-YYYY parameters and tries to pull info between the first day of the month for param1 and the last day of the month for param2 and ended up having to set my date boundaries as
LocalDate startDate = new LocalDate(1, param1.getMonth(), param2.getYear()); //pretty straightforward, right?
//bump month by one, account for rollover, set endDate to the first of that month, then subtract one day
int endMonth = param2.month == 12 ? param2.month + 1 : 1;
LocalDate endDate = new LocalDate(1, endMonth, param2.year).minusDays(1);
This is extraordinarily simply for humans to understand intuitively, but to code it requires accounting for a bunch of backward edge/corner case garbage. The answer, of course, is to train humans to think in Unix epoch time.
Unix epoch time is wrong too, as it doesn’t include leap seconds, meaning your time difference will be off by up to 15 seconds.
