Comment by weinzierl
3 days ago
For thousands of years, we used time synchronized to the sun, with flexible intervals. That’s the natural thing for a lot of things, and that is what UTC is for.
Now, if you don’t care about the sun but about fixed intervals, you can always use TAI.
Standards are there to serve people, and we should have the choice to use the standard that fits our needs best. Changing the meaning of a standard retroactively, with no good reason and when a good alternative is available, is nothing short of irresponsible.
For thousands of years, we used time synchronized to the sun to some approximation that was off by minutes, not microseconds, and nobody cared if the current time relative to the sun was off by a second because they had no way of actually determining that. And then some jerk came along and invented computers and precision timekeeping and suddenly things depended on things like time not appearing to move backwards by as much as a second. :)
UTC is still fixed to the sun. Without leap seconds, it will be hundreds of years before the divergence between UTC and the sun is perceptible in daily life. Even then, I can't think of anything where that would matter.
I think there is a good alternative available, UT1. UTC was always divergent from UT1 anyway, so this change shouldn't affect anyone who actually needs precise solar timekeeping.
More importantly, there are many good reasons to drop leap seconds, such as the massive increase in complexity they impose on all time-related code.
Standards should serve people, which is why leap seconds should never have existed. Imagine: "Sure some airliners crashed, and half the internet went offline for a couple days, but if you drive to the right longitude line, the sun will be exactly overhead at 12:00:00, and here in town it's overhead at 12:23:48. That's worth anything. I'd hate to live in a world where it was overhead at 12:23:49, or that'd be over my great-great-great grandchildren at 12:23:47."
The promise of UTC is bounded deviation from solar time while keeping the intervals of ISO seconds. I think this is a valuable trade-off that should continue to exist.
> I think this is a valuable trade-off that should continue to exist.
And it has, the bound on the deviation was increased slightly to 3600 seconds
I'd prefer if dUT1 was restored to ±.9s after NTP rollover in 2036, Y2K38, and GPS week rollover in 2038. This way we now know precisely what the UTC times will be for those events and dUT1 probably will be <10s at that point. Software will need to deal with times like 23:59:63 properly by then (too much still can't handle 23:59:60 leap seconds yet). Maybe we could have dUT1 < ±9.9s going forward.
The problems with letting dUT1 > 1800 and above is that well before that it starts mattering for almost everything and then you have to consult the solution (here's just 2025's):
That's generated by the US Navy for all intents and is way more data than used now for leap seconds which are fine enough of a granularity for most things. Future timestamps in UT1 will get difficult to handle as well. Previously software could assume it knew to the closest second which was often good enough.
I'm not sure if I completely follow you, but I'd like to ask: Why is it a problem if there's a divergence between UT1 and UTC? Besides astronomers, who cares if the sun is directly overhead a few minutes later than it "should" be?
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Nope, the whole point of this is to remove the coupling for UTC. You can either have monotonic time (or at least per-observer monotonic time), or you can follow earth's rotation. Choosing monotonic time is perfectly fine (and feel free to pick your epoch and time unit), but like we have timezones such that 12:00 means something (mostly), having the human conception of what time means does imply that we do kinda need to look at what's happening outside.
We have GMT for standardised solar time. I assume there were good reasons for moving to UTC? Either is fine for many purposes.
So, the thing you probably want for "standardized solar time" is named UT1, there are a bunch of complicated technical details here, which do not matter, but ultimately UT0 and UT2 are not relevant to normal people, UT1 is a hypothetical solar time, estimated by observatories, and UTC is the world's civil time, now fixed to TAI plus 37 seconds.
GMT (Grenwich Mean Time) is a legacy from when Britain (and thus Grenwich, an observatory in London, England) was more important. These days GMT, even in British legislation, just means UTC. When we say "In the winter we use GMT not BST" we're not switching to or from some archaic time system, GMT is just defined as UTC+0 and BST is defined as UTC+1 the same way summer time zones work in several others places which have them.
GP wanted solar time, so that would be old style GMT, which would be now UT1, right?
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