4 ms·

Riffing on “if it’s painful, do it more often”, I wonder if mandatory leap seconds every year, but trueing up the delta from N years ago, would be a good compro

Riffing on “if it’s painful, do it more often”, I wonder if mandatory leap seconds every year, but trueing up the delta from N years ago, would be a good compromise? Regularity makes it easier to plan, and 6 months’ notice is not really enough for many OS distribution paths (eg IoT, embedded). Since the list of delta updates is queued, you could bake N years of updates into your system if it’s a fire-and-forget OS. A number in between 5 and 10 seems reasonable to me, but seeing as we are discussing living with 50 years of drift it could be higher. And sure, for this to work, allow non-integer deltas again; or just have a rule that you round the applied adjustment down. Seems no harder to bake in the last 50 years of leap seconds as to include to Olson TZ database in your distro.

lifthrasiir 2y ago
That's actually a good idea in the short term (i.e. less than one century). The length of the day (LOD) is thought to be linearly increasing in the long term though, so ΔT, the cumulative difference between past SI days and actual LOD, should be quadratically increasing and a delayed leap second adjustment would be too slow to catch up at some point in the future. Yet another possibility is to put any possible kind of leap second at the beginning of the year. The only requirement set by past CGPMs is that dUTC = UT1 - UTC should be in [-0.9, +0.9] seconds, so we can always put a positive leap second when dUTC is in [-0.9, -0.1]s and a negative leap second when dUTC is in [+0.1, +0.9]s, dramatically increasing the number of leap seconds without violating the dUTC requirement. If the dUTC requirement is a bit more relaxed (say, [-2, +2] seconds) then we can even mandate leap second every year! But well no, I'm strongly against the current form of leap seconds because it is already problematic in the short term and will be yet useless in the long term. Recall that ΔT is expected to be quadratically increasing in the long term; this means that the effectiveness of leap seconds is limited to the point when any small fixed number of leap seconds per year (12 in the current system, but anything larger than 1 will cause a problem) is no longer sufficient, and that point is not far from the point where the magnitude of ΔT is significantly large and leap seconds are absolutely required. As DST demonstrates, the world is probably fine with ~2,000 seconds of ΔT, which wouldn't happen before 2500, but at that point we would already start using double leap seconds per year at average. We would probably abolish leap seconds for that reason alone.
ncruces 2y ago
If you go with that, just move it in the correct direction every year, regardless if you make the absolute delta bigger (you'll fix it in a year by going backwards). If this is not enough to ping-pong around the correct result, because you're drifting too fast, just increase the rate of changes, now that the system is well oiled. That said, we should not have leap seconds, just timezones around TAI. If UTC wants to be a timezone that changes every six months with a second offset, so be it. Bureaucratic systems are already in place to solve that.

lifthrasiir 2y ago

That's actually a good idea in the short term (i.e. less than one century). The length of the day (LOD) is thought to be linearly increasing in the long term though, so ΔT, the cumulative difference between past SI days and actual LOD, should be quadratically increasing and a delayed leap second adjustment would be too slow to catch up at some point in the future. Yet another possibility is to put any possible kind of leap second at the beginning of the year. The only requirement set by past CGPMs is that dUTC = UT1 - UTC should be in [-0.9, +0.9] seconds, so we can always put a positive leap second when dUTC is in [-0.9, -0.1]s and a negative leap second when dUTC is in [+0.1, +0.9]s, dramatically increasing the number of leap seconds without violating the dUTC requirement. If the dUTC requirement is a bit more relaxed (say, [-2, +2] seconds) then we can even mandate leap second every year! But well no, I'm strongly against the current form of leap seconds because it is already problematic in the short term and will be yet useless in the long term. Recall that ΔT is expected to be quadratically increasing in the long term; this means that the effectiveness of leap seconds is limited to the point when any small fixed number of leap seconds per year (12 in the current system, but anything larger than 1 will cause a problem) is no longer sufficient, and that point is not far from the point where the magnitude of ΔT is significantly large and leap seconds are absolutely required. As DST demonstrates, the world is probably fine with ~2,000 seconds of ΔT, which wouldn't happen before 2500, but at that point we would already start using double leap seconds per year at average. We would probably abolish leap seconds for that reason alone.

ncruces 2y ago

If you go with that, just move it in the correct direction every year, regardless if you make the absolute delta bigger (you'll fix it in a year by going backwards). If this is not enough to ping-pong around the correct result, because you're drifting too fast, just increase the rate of changes, now that the system is well oiled. That said, we should not have leap seconds, just timezones around TAI. If UTC wants to be a timezone that changes every six months with a second offset, so be it. Bureaucratic systems are already in place to solve that.