4 ms·

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 b

by krick 4y ago

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. For whatever reason (for obvious reasons that is, but doesn't matter) UTC was chosen in virtually any software system to keep time. So, ok, if there is a suspicion of leap seconds being unnecessary. How about moving from UTC time to TAI then? Let's keep UTC as it is, keep adding leap seconds and just make it a best practice to rely on TAI for all datetime operations and world clock synchronization? Maybe it will work out, maybe it won't, but at least you won't be breaking a perfectly working alternative (currently — mainstream) system. The more I think about it, the more outrageously stupid abolishing leap seconds seems.

slavik81 4y ago
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.
- lifthrasiir 4y ago
  It is worthwhile to look at the past; before leap seconds the disagreement with UT1 was handled by changing the rate of UTC slightly, and that's probably even worse than leap seconds. And for a while the unit of adjustment was less than a second, varying from 0.05 to 0.2 seconds. I believe enough people have complained about subsecond adjustments, and thus leap seconds have survived only because not enough people have complained at that time.
- krick 4y ago
  Because a minute is a huge amount of time (and, by the way, don't forget, that minutes don't exist, I just understand that you mean 60 seconds) and there is no such thing as "leap milliseconds" because UTC is literally just counting seconds. Basically, UT1 already is an implementation of what you call "leap milliseconds". Not literally, but achieves the same thing. And it is way too complicated to use it in practice outside of astronomy-specific tasks. So, to sum it up: - TAI is a real thing, it has a concrete meaning, and it's "leap infinity". - UT1 is a real thing, but is unusable in practice, and you could think of it as "leap ms" - UTC until yesterday was a real thing, meaning time, which has seconds equal to TAI-seconds, but not drifting from UT1 for more than 0.9 s. Since today it's broken and I'm not sure what it even means anymore — I mean, not in practice, but "platonically". - Nobody just introduced a standard that would mean "time with seconds equal to TAI-seconds, but not drifting from UT1 for more than 59 s" yet. I guess you could be the one to do it, but I'm not sure it would get a wide adoption.
  - eternityforest 4y ago
    Why is UT1 unusable? Can we approximate it with something like a polynomial that gets updated periodically?
dwheeler 4y ago
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.
- doctor_eval 4y ago
  Surely it’s all the test firings of Merlin and Raptor engines that’s slowing the earth down in the first place? I mean first he screws up twitter, now it’s time itself. (/s)
  - joadha 4y ago
    He is absolutely, singlehandedly destroying Twitter-- no sarcasm.
- varajelle 4y ago
  > its rotation will stay at exactly 24 hours. The earth rotate around itself in 23 hours and 56 minutes https://en.m.wikipedia.org/wiki/Sidereal_time https://en.m.wikipedia.org/wiki/Sidereal_time
  - krick 4y ago
    It rotates itself in 23 hours and 56 minutes relative to the fixed stars. It rotates itself in 24 hours relative to the Sun. It is Earth's rotation relative to the Sun what people care about in most situations, because day and night depend on that, not on the position relative to some far-away stars.
    - huslage 4y ago
      24 hours is an average over the duration of the Earth's orbit around the sun.
      - 4y ago
toast0 4y ago
> For whatever reason (for obvious reasons that is, but doesn't matter) UTC was chosen in virtually any software system to keep time. What was chosen really isn't UTC. Several UTC seconds in the past are not accurately representable in unixtime. Several unixtime seconds in the past are ambigious as to which UTC second they are. Unixtime is awfully close to UTC time, but it's not the same. If UTC time stops inserting leap seconds and never has negative leap seconds, then they will be equivalent going forward.
- deleted 4y ago
  [deleted]
- krick 4y ago
  Not really. I mean, it's true that we should distinguish between the 2 and everything that you said about the difference is also true. But unixtime doesn't really "exist" in a sense UTC and TAI do. It is rather an imperfect implementation of UTC, that chooses to ignore (or repeat) some seconds. You can hear that unixtime is the number of seconds passed since X. But it isn't really true though. The number of seconds is number of seconds, it isn't defined by our standards, it just exists. And TAI is a fair representation of how many seconds on Earth actually passed (on average) since whatever. UTC kinda does it as well by virtue of 1 second being equal to 1 TAI second, but it actually counts (counted until yesterday) the number of Earth's rotations. It's just every rotation (represented by 24H) sometimes consists of more than 86 400 seconds. Unixtime on each individual device counts nothing. It imperfectly represents UTC timestamp received over NTP. Some timestamps are represented twice by the same value. Of course, you can just put your device offline and call it "unixtime" whatever number of seconds it counts since any moment, but you know it will drift away from any meaningful "real" time soon enough. (Also, it's not even entirely fair to say, as you did, that it is unixtime that was chosen by all the software. Many programs store datetimes as strings. Usually, they still don't support "23:59:60" anyway, but that doesn't really make them unixtime. Unixtime is a timestamp encoding.) So, that's basically what I'm talking about: you can just make unixtime an implementation of TAI (as opposed to UTC). You can build a new calendar format for it, introduce a new name (not UTC!) for it and see how well it does when all the world slowly drift from Earth's rotation to keep up with TAI. Maybe it actually is fine, I'm not a judge for it (because it really is complicated and I didn't decide yet if it's a good solution or not). But why the fuck would you destroy UTC for it?! It is a closest usable representation of UT1, which doesn't stop to exist! Leave it be!
naniwaduni 4y ago
Consider that the most widely deployed time standard outside the UT framework is GPS time, which was initially synced with UTC but is de facto TAI-19, because it turns out that constant-rate monotonic time is useful and UTC fails at even the alleged astronomical use-case.
quickthrower2 4y ago
Pretty sure you are saying the same thing as the post you replied to. They are recommending TAI for storage, compute, and not against UTC for human consumption Although the easier hack: Abolish leap seconds from UTC!

by krick 4y ago

slavik81 4y ago

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.

lifthrasiir 4y ago
It is worthwhile to look at the past; before leap seconds the disagreement with UT1 was handled by changing the rate of UTC slightly, and that's probably even worse than leap seconds. And for a while the unit of adjustment was less than a second, varying from 0.05 to 0.2 seconds. I believe enough people have complained about subsecond adjustments, and thus leap seconds have survived only because not enough people have complained at that time.
krick 4y ago
Because a minute is a huge amount of time (and, by the way, don't forget, that minutes don't exist, I just understand that you mean 60 seconds) and there is no such thing as "leap milliseconds" because UTC is literally just counting seconds. Basically, UT1 already is an implementation of what you call "leap milliseconds". Not literally, but achieves the same thing. And it is way too complicated to use it in practice outside of astronomy-specific tasks. So, to sum it up: - TAI is a real thing, it has a concrete meaning, and it's "leap infinity". - UT1 is a real thing, but is unusable in practice, and you could think of it as "leap ms" - UTC until yesterday was a real thing, meaning time, which has seconds equal to TAI-seconds, but not drifting from UT1 for more than 0.9 s. Since today it's broken and I'm not sure what it even means anymore — I mean, not in practice, but "platonically". - Nobody just introduced a standard that would mean "time with seconds equal to TAI-seconds, but not drifting from UT1 for more than 59 s" yet. I guess you could be the one to do it, but I'm not sure it would get a wide adoption.
- eternityforest 4y ago
  Why is UT1 unusable? Can we approximate it with something like a polynomial that gets updated periodically?

dwheeler 4y ago

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.

doctor_eval 4y ago
Surely it’s all the test firings of Merlin and Raptor engines that’s slowing the earth down in the first place? I mean first he screws up twitter, now it’s time itself. (/s)
- joadha 4y ago
  He is absolutely, singlehandedly destroying Twitter-- no sarcasm.
varajelle 4y ago
> its rotation will stay at exactly 24 hours. The earth rotate around itself in 23 hours and 56 minutes https://en.m.wikipedia.org/wiki/Sidereal_time https://en.m.wikipedia.org/wiki/Sidereal_time
- krick 4y ago
  It rotates itself in 23 hours and 56 minutes relative to the fixed stars. It rotates itself in 24 hours relative to the Sun. It is Earth's rotation relative to the Sun what people care about in most situations, because day and night depend on that, not on the position relative to some far-away stars.
  - huslage 4y ago
    24 hours is an average over the duration of the Earth's orbit around the sun.
    - 4y ago

toast0 4y ago

> For whatever reason (for obvious reasons that is, but doesn't matter) UTC was chosen in virtually any software system to keep time. What was chosen really isn't UTC. Several UTC seconds in the past are not accurately representable in unixtime. Several unixtime seconds in the past are ambigious as to which UTC second they are. Unixtime is awfully close to UTC time, but it's not the same. If UTC time stops inserting leap seconds and never has negative leap seconds, then they will be equivalent going forward.

deleted 4y ago
[deleted]
krick 4y ago
Not really. I mean, it's true that we should distinguish between the 2 and everything that you said about the difference is also true. But unixtime doesn't really "exist" in a sense UTC and TAI do. It is rather an imperfect implementation of UTC, that chooses to ignore (or repeat) some seconds. You can hear that unixtime is the number of seconds passed since X. But it isn't really true though. The number of seconds is number of seconds, it isn't defined by our standards, it just exists. And TAI is a fair representation of how many seconds on Earth actually passed (on average) since whatever. UTC kinda does it as well by virtue of 1 second being equal to 1 TAI second, but it actually counts (counted until yesterday) the number of Earth's rotations. It's just every rotation (represented by 24H) sometimes consists of more than 86 400 seconds. Unixtime on each individual device counts nothing. It imperfectly represents UTC timestamp received over NTP. Some timestamps are represented twice by the same value. Of course, you can just put your device offline and call it "unixtime" whatever number of seconds it counts since any moment, but you know it will drift away from any meaningful "real" time soon enough. (Also, it's not even entirely fair to say, as you did, that it is unixtime that was chosen by all the software. Many programs store datetimes as strings. Usually, they still don't support "23:59:60" anyway, but that doesn't really make them unixtime. Unixtime is a timestamp encoding.) So, that's basically what I'm talking about: you can just make unixtime an implementation of TAI (as opposed to UTC). You can build a new calendar format for it, introduce a new name (not UTC!) for it and see how well it does when all the world slowly drift from Earth's rotation to keep up with TAI. Maybe it actually is fine, I'm not a judge for it (because it really is complicated and I didn't decide yet if it's a good solution or not). But why the fuck would you destroy UTC for it?! It is a closest usable representation of UT1, which doesn't stop to exist! Leave it be!

naniwaduni 4y ago

Consider that the most widely deployed time standard outside the UT framework is GPS time, which was initially synced with UTC but is de facto TAI-19, because it turns out that constant-rate monotonic time is useful and UTC fails at even the alleged astronomical use-case.

quickthrower2 4y ago

Pretty sure you are saying the same thing as the post you replied to. They are recommending TAI for storage, compute, and not against UTC for human consumption Although the easier hack: Abolish leap seconds from UTC!