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The leap second’s time is up: world votes to stop pausing clocks

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Re: The leap second’s time is up: world votes to stop pausing clocks

#181

Post by layer8 »

finnh wrote: post #97

> The CGPM — which also oversees the international system of units (SI) — has proposed that no leap second should be added for at least a century, allowing UT1 and UTC to slide out of sync by about 1 minute. So, in one century, we'll get 1 minute's worth of drift. Recall that we all share the same clock within timezones, and 1 minute of drift between atomic & solar clocks is the equivalent of traveling 1/60th of your…

The problem is mostly (or so I’ve heard) that the drift is relevant for astronomical applications, and they rely on time dissemination which is done in UTC. If UTC decides to start deviating from TAI by dropping leap seconds, those applications will be in trouble. I’m sure that the problem is overblown, but this is the reasoning that was put forward in the past.

Re: The leap second’s time is up: world votes to stop pausing clocks

#182

Post by slavik81 »

krick wrote: post #166
techdragon wrote: post #80

Hot take… Storing anything as UTC was a mistake and we should be using TAI for all storage and computation, only transforming into more human friendly formats for display to end users. This never needed to be a problem except we decided to make it harder to use TAI than UTC and so everything got built up off the backs of legacy bios level hardware supported UTC style clock behaviour, when we should have been using TA…

I'm not sure I support your "hot take" — it is hot and requires a lot of contemplation. But that's not the point, IMO. The point is, that there ALREADY EXIST both TAI and UTC. TAI is true monotonic (whatever it means in a relativistic universe) and doesn't make any compromises. UTC abolishes monotonicity in order to keep both the length of a second and the time relationship to the orbital rotation. They both work. Fo…

If you want to keep UTC matching the solar rotation, why do you specifically require leap seconds? Why not leap minutes? Or leap milliseconds? The choice of ±1 s as the acceptable error seems arbitrary.

Re: The leap second’s time is up: world votes to stop pausing clocks

#183

Post by Strom »

Epa095 wrote: post #147
zokier wrote: post #127

Earlier quoted context omitted.

I'm pretty sure UTC is monotonic too, its unix timestamps that really are the true mess

Yeah you are right, when a leap second is introduced it becomes 23:59:60 (monotonic) in utc, while with unix-time a normal way to handle it is to repeat 23:59:59 twice (non-monotonic).

Leap seconds can be negative.

Re: The leap second’s time is up: world votes to stop pausing clocks

#184

Post by alerighi »

I never really understood why we need leap seconds. Or better: why we need to bother with them in a computer system at lower level.

If we decide that we absolutely need to keep our time in sync with the rotation of the earth, really what should be done is define a timezone with all the leap seconds applied, and use that timezone to only display it to the end user. Not change the way we sync computer clocks for no reason! NTP shouldn't contemplate leap seconds, for example...

Re: The leap second’s time is up: world votes to stop pausing clocks

#185

Post by capitainenemo »

nostromo wrote: post #101
adamsb6 wrote: post #50

Currently software has to be built to accommodate leap seconds. They happen frequently enough that you'll find out within a few years whether your software breaks when time suddenly skips forward or backward. If we kick the can down the road such that eventually we'll need to add a leap minute, we're going to end up with software that was never written to expect time to change in such a way, hasn't had a real world t…

Nobody really cares about clocks being celestially "off" by a minute either. So this isn't a once-a-century thing, it's adding-a-leap-15-minutes-once-a-millenia issue.

https://royalsocietypublishing.org/doi/10.1098/rspa.2016.040...

Odd. I was wondering how fast it actually was long term, and this rate from historical record seems much lower. They cite 1.8ms/century if I'm reading it correctly with some odd cyclical thing going on. " the change in the length of the mean solar day (lod) increases at an average rate of +1.8 ms per century. "

I mean, we've added 22 seconds over 50 years. Although at current rate it would still just be 7 minutes after a millenia :)

edit You know, nevermind, that's all covered on wikipedia. https://en.wikipedia.org/wiki/Leap_second#Slowing_rotation_o...

Re: The leap second’s time is up: world votes to stop pausing clocks

#186

Post by gpvos »

thfuran wrote: post #95
bombcar wrote: post #84

Earlier quoted context omitted.

I've always thought that the best way would just have leap seconds every six months, and have it be ± 1 second no matter what - so sometimes you'd go back a second twice in a row, and then go forward a second to get back to correct. That'd test all the software paths.

Making time less accurate just for the sake of testing in production doesn't seem great.

From 2035 it's going to be less accurate in exactly the same way. I'd argue bombcar's method is more robust.

I don't know of anything that actually requires UTC to be within 1 second of average rotation-based time; having it within 2 or 3 seconds is extremely unlikely to actually break anything. But we do generally want to have measured time roughly in line with Earth time in the medium to long term.

Re: The leap second’s time is up: world votes to stop pausing clocks

#187

Post by alerighi »

ars wrote: post #13

So we make things worse for humans in order to make it easier for computers? Yah, one second doesn't matter, but it builds up. This: "Or we could even decouple our sense of time from the Sun entirely, to create a single world time zone in which different countries see the Sun overhead at different times of day or night." Shows that they are completely disconnect from human reality: "Science already doesn’t use local…

Because we have to distinguish the two concepts. With timezones we already did it: computers save time (usually) in UTC format, and time is converted to the user time zone only when displaying it (at an higher level).

This is obviously better, when you save a file for example you don't care about the region of the user, and thus the save timestamp of the file should really be an absolute number, so if you take your laptop and go from one country to another your whole system doesn't break because it sees timestamps in the future, same thing when daylight saving is applied and the clock is brought back/forward by an hour.

Leap seconds, if we decide that we should keep them (to me not, because the difference is so little that we would start to notice that in centuries, and who knows not which computer systems we will have but if humanity still exists), should really be handled at time zone level, by shifting of an offset that contemplates leap seconds, and not by slowing up/accelerating clocks.

Re: The leap second’s time is up: world votes to stop pausing clocks

#188

Post by dwheeler »

krick wrote: post #166
techdragon wrote: post #80

Hot take… Storing anything as UTC was a mistake and we should be using TAI for all storage and computation, only transforming into more human friendly formats for display to end users. This never needed to be a problem except we decided to make it harder to use TAI than UTC and so everything got built up off the backs of legacy bios level hardware supported UTC style clock behaviour, when we should have been using TA…

I'm not sure I support your "hot take" — it is hot and requires a lot of contemplation. But that's not the point, IMO. The point is, that there ALREADY EXIST both TAI and UTC. TAI is true monotonic (whatever it means in a relativistic universe) and doesn't make any compromises. UTC abolishes monotonicity in order to keep both the length of a second and the time relationship to the orbital rotation. They both work. Fo…

Eliminating leap seconds was only a half measure. They should have finished the job by adding rockets to the Earth to ensure that its rotation will stay at exactly 24 hours.

If they weren't going to do that, then why eliminate leap seconds? Kicking the problem down the road doesn't really solve the problem, it just makes it worse later.

Re: The leap second’s time is up: world votes to stop pausing clocks

#189

Post by xwolfi »

hcrisp wrote: post #115
hoytech wrote: post #103

In 2015 I was working at a "fintech" company and a leap second was announced. It was scheduled for a Wednesday, unlike all others before which had happened on the weekend, when markets were closed. When the previous leap second was applied, a bunch of our Linux servers had kernel panics for some reason, so needless to say everyone was really concerned about a leap second happening during trading hours. So I was assig…

Reminds me of the story of the computer engineer at Data General in Traccy Kidder's nonficion book, "The Soul of a New Machine" [0], who quit after spending weeks toiling away on sub-second timing concerns: > He went away from the basement and left this note on his terminal: "I'm going to a commune in Vermont and will deal with no unit of time shorter than a season." [0] https://en.m.wikipedia.org/wiki/The_Soul_of_a_…

What should I say, trying to go sub millisecond, one profiling run at a time, sigh...

Re: The leap second’s time is up: world votes to stop pausing clocks

#190

Post by jimmaswell »

svara wrote: post #138
hoytech wrote: post #103

In 2015 I was working at a "fintech" company and a leap second was announced. It was scheduled for a Wednesday, unlike all others before which had happened on the weekend, when markets were closed. When the previous leap second was applied, a bunch of our Linux servers had kernel panics for some reason, so needless to say everyone was really concerned about a leap second happening during trading hours. So I was assig…

The moral of the story is that laziness is a virtue. Think of all the time that could have been saved, had you had no plans like your partners ;)

Think of all the time that could be better appropriated than on fintech in general. Seems like such a waste of resources siccing a bunch of computers against each other in a zero sum game of stock arbitrage. I will admit some of the stuff tech comes out of it is cool on its own at least.
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