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Insane complexity of calendrically correct date and time operations

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Re: Insane complexity of calendrically correct date and time operations

#141

Post by sla29970 »

bloak wrote: post #120
repolfx wrote: post #117

Earlier quoted context omitted.

But offset of UTC for TAI is like 37 seconds or something poxy like that. Nobody cares about this, the sun moves too slowly for that to make any difference. There's been talk of setting UTC=TAI for quite a long time and I think it'd make sense. It'd take so long for TAI to drift from the actual rising and setting of the sun that we'd probably all have standardised on Swatch Beats by then anyway.

Yes, the difference is 37 seconds now, but it's growing quadratically. It's quite possible that we'll change the way we express times and dates, but it's almost certain that we'll want them to stay in phase with the sun, and we'll probably want to stick with the SI second and with something like TAI. My guess is we'll continue to want a simple relationship between TAI (or its successor) and the civil clock time, some…

In 1950 astronomers pointed out that there would have to be two kinds of time, one to agree with calendar days and one to be as uniform as possible. Arguments over subsequent decades inexplicably decided that there could only be one kind of time specified by international agreements, and we ended up with a choice of two out of three characteristics in what we now call UTC. https://www.ucolick.org/~sla/leapsecs/picktwo.html

Re: Insane complexity of calendrically correct date and time operations

#142

Post by AllegedAlec »

disillusion wrote: post #135
AllegedAlec wrote: post #90

Earlier quoted context omitted.

> Wow. I live in Europe, and find it weird that people can consider the week to start on Sunday. Netherlands reporting in. My parents always taught me that the week starts on Sunday.

Funny, I'm Dutch and I learned the week starts on Monday. Well, except for strongly religious families.

My parents were pretty religious in their youths, and were from conservative parts of the country. Perhaps that has something to do with it.

Re: Insane complexity of calendrically correct date and time operations

#143

Post by zokier »

sla29970 wrote: post #141
bloak wrote: post #120

Earlier quoted context omitted.

Yes, the difference is 37 seconds now, but it's growing quadratically. It's quite possible that we'll change the way we express times and dates, but it's almost certain that we'll want them to stay in phase with the sun, and we'll probably want to stick with the SI second and with something like TAI. My guess is we'll continue to want a simple relationship between TAI (or its successor) and the civil clock time, some…

In 1950 astronomers pointed out that there would have to be two kinds of time, one to agree with calendar days and one to be as uniform as possible. Arguments over subsequent decades inexplicably decided that there could only be one kind of time specified by international agreements, and we ended up with a choice of two out of three characteristics in what we now call UTC. https://www.ucolick.org/~sla/leapsecs/picktw…

You website is a true hidden gold nugget, thanks for putting in the time to write all that up.

As an expert (as far as anyone around here is), what would your pick be for common civil time? Personally I feel like "precise time and simplicity" is almost obvious choice, but apparently it is not quite that clear cut.

Re: Insane complexity of calendrically correct date and time operations

#144

Post by bloak »

zokier wrote: post #143
sla29970 wrote: post #141

Earlier quoted context omitted.

In 1950 astronomers pointed out that there would have to be two kinds of time, one to agree with calendar days and one to be as uniform as possible. Arguments over subsequent decades inexplicably decided that there could only be one kind of time specified by international agreements, and we ended up with a choice of two out of three characteristics in what we now call UTC. https://www.ucolick.org/~sla/leapsecs/picktw…

You website is a true hidden gold nugget, thanks for putting in the time to write all that up. As an expert (as far as anyone around here is), what would your pick be for common civil time? Personally I feel like "precise time and simplicity" is almost obvious choice, but apparently it is not quite that clear cut.

"Simplicity" is rather subjective, even if you answer the question: simple for who?

Civil time has to stay in phase with the sun. As I see it, that's not negotiable. Inserting leap seconds, so that the nanosecond field of UTC remains the same as the nanosecond field of TAI, and the jumps that occur are negligible for ordinary people, seems to me overall the simplest solution, though I can see that UTC-SLS would be simpler for some people in some situations, and switching to leap minutes or leap hours would be simpler for people living now, who could then just ignore the problem. (Pollution and global warming and lots of other things can be treated in the same way, of course. Perhaps some of these things really will be easier to solve in the future, but I'd rather not rely on it.)

Re: Insane complexity of calendrically correct date and time operations

#145

Post by zokier »

bloak wrote: post #144
zokier wrote: post #143

Earlier quoted context omitted.

You website is a true hidden gold nugget, thanks for putting in the time to write all that up. As an expert (as far as anyone around here is), what would your pick be for common civil time? Personally I feel like "precise time and simplicity" is almost obvious choice, but apparently it is not quite that clear cut.

"Simplicity" is rather subjective, even if you answer the question: simple for who? Civil time has to stay in phase with the sun. As I see it, that's not negotiable. Inserting leap seconds, so that the nanosecond field of UTC remains the same as the nanosecond field of TAI, and the jumps that occur are negligible for ordinary people, seems to me overall the simplest solution, though I can see that UTC-SLS would be si…

> "Simplicity" is rather subjective, even if you answer the question: simple for who?

I used simplicity in the meaning provided by link in parent comment refering to three desirable properties of time systems: "Every "day" has 86400 "seconds" (606024)."

> Civil time has to stay in phase with the sun. As I see it, that's not negotiable.

I don't see why that needs to be the case on a seconds level.

> switching to leap minutes or leap hours would be simpler for people living now, who could then just ignore the problem. (Pollution and global warming and lots of other things can be treated in the same way, of course. Perhaps some of these things really will be easier to solve in the future, but I'd rather not rely on it.)

Considering that need for leap hour would appear in over 500 years, I feel like trying predict the situation then is really borderline overarrogant.

Also leap hour would be basically a timezone shift, and I bet we will be doing timezone changes anyways in the next 500 years

Re: Insane complexity of calendrically correct date and time operations

#146

Post by bloak »

zokier wrote: post #145
bloak wrote: post #144

Earlier quoted context omitted.

"Simplicity" is rather subjective, even if you answer the question: simple for who? Civil time has to stay in phase with the sun. As I see it, that's not negotiable. Inserting leap seconds, so that the nanosecond field of UTC remains the same as the nanosecond field of TAI, and the jumps that occur are negligible for ordinary people, seems to me overall the simplest solution, though I can see that UTC-SLS would be si…

> "Simplicity" is rather subjective, even if you answer the question: simple for who? I used simplicity in the meaning provided by link in parent comment refering to three desirable properties of time systems: "Every "day" has 86400 "seconds" (60 60 24)." > Civil time has to stay in phase with the sun. As I see it, that's not negotiable. I don't see why that needs to be the case on a seconds level. > switching to lea…

Not at all. Just because it involves an "hour", rather than a "second", doesn't mean that it resembles a "timezone shift". It's totally different.

With a timezone shift, all that happens is that "09:00:00 +0900" is the same as "10:00:00 +1000". We can cope with that. But if you make UTC jump back an hour, then we have "09:59:59 +1000" followed by "09:00:00 +1000", and then the whole previous hour happens again. The internal timestamps in computer systems (typically expressed as a number of seconds since some epoch) repeat themselves for an hour. Causality is violated. Most computers stop working. You would probably have to switch them off beforehand to prevent data loss and even longer interruptions to service. You could shut down all the servers and desktop machines, stop all public transport and so on, but you can't just turn off the computers in embedded systems and satellites and so on...

So let's not try to arrogantly predict the situation in 500 years. Let's carry on with the established system of leap seconds, at least until someone comes up with a sensible alternative. Then there won't be a "situation" in (less than) 500 years.

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