I thought that was the plan when they decided to give up on leap seconds.
I don't get the insistence on keeping nominal seconds-alignment (or even minutes-alignment) between the clock and the sun's position; we already don't experience it in practice.
Timezone regions are fudged all over the world[1] for political and practical reasons, but even if they weren't, people living near one timezone edge don't experience the "sun noon" at the same time as people living near the other edge, even though they share the same clock time.
It has nothing to do with time zones. People can deal with weird time keeping practices, but distributed software systems can become completely borked. It's happened before in all sorts of different ways. Transaction order can get messed up. Event queues can drop or duplicate events. Obviously, it's a big problem, otherwise people wouldn't be so intent on getting rid of them. And having a leap hour instead of a leap second would be a whole order of magnitude worse, especially if it occurs after hundreds or thousands of years of people writing software that's oblivious to the phenomenon.
But completely getting rid of leap seconds for UTC is misguided. We already have TAI, which is literally just UTC without leap seconds. If leap seconds are messing with your system, just use TAI. Don't make UTC a slightly worse version of TAI.
Civil society around the world has decided on UTC as the basis for time. What’s easier, convincing everyone to switch to TAI or changing the definition of UTC? I would guess it’s the latter.
> It has nothing to do with time zones. [...] And having a leap hour instead of a leap second would be a whole order of magnitude worse [...]
The idea is exactly to not have a leap hour, UTC is kept completely untouched. Everyone changes their timezone instead, exactly like we already do with daylight savings, except this would happen only once every few thousands of years instead of twice a year.
Well the current plan according to the BIPM is to keep adjusting UTC, but with bigger and less frequent adjustments. I'm predicting they'll change course in a hundred years, as you say, and just give up on leap seconds/minutes/hours altogether. So yes, I agree that this is the most likely scenario.
But again, we already have a time system that does not have leap seconds/minutes/hours. TAI and UTC would become effectively redundant. I don't understand why we need another version of TAI.
I agree with everything you said, I just don't see why we need both UTC and TAI. That is, I don't understand why we insist on keeping UTC synchronized with Earth's orientation.
On the one hand (like you said before), UTC is what we use for stuff like ordering transactions, which has absolutely nothing to do with the position of the Sun in the Sky.
And on the other hand, we already use timezones to reconcile the rough position of the Sun with our universal clock. Timezones only have resolution of 1 hour (or half in very few places), but looking at how fudged a lot them are, people don't really seem to care. I mean, look at Argentina, which fits almost perfectly in UTC-4 but chooses to use UTC-3 instead. China is even crazier, using a single time in its whole territory which could easily have 3 or 4 different timezones.
At it's core, UTC is about reconciling 2 different clocks; the Earth (basically represented by UT1) and the Cesium atom (represented by TAI). It's a useful basis for Civil time -- which is naturally political -- because everybody seems to intuitively agree that seconds should be defined by the Cesium standard but days should be aligned with the Earth's rotation. It's not guaranteed that all governments would pick the same if forced to pick only one of the two. That would make time zones even harder.
Sure, people in Western China may regularly see the sun at midnight, but that's not without controversy. People generally like the sun to be out when they're up.
So I think it makes sense to have both UTC and TAI. If the BIPM just turns UTC into TAI plus a constant offset, then I'd wager they would eventually introduce another system to take the place of the former UTC, with leap seconds, so some people can have that system that reconciles the two clocks if they want it. It's hard to predict the future. But the reasoning in the GCPM resolution [1] seems inherently flawed to me. "recalling that the CGPM at its 26th meeting (2018) ... stated that UTC is the only recommended time scale for international reference" is the core of the problem. TAI should be the ultimate basis. UTC is based on TAI (with leap seconds), and civil time based on UTC.
Time can only be measured by clocks (oscillatory systems). It's a slippery concept for which humans have a natural, flawed intuition. But if you understand your clock(s) really well, then timekeeping makes perfect sense. There's just a lot of clocks around. There's Unix time, UTC, TAI, smeared UTC, stop-the-clock UTC, UT1, and lots of others. Make sure you understand the clocks your system is using and how they relate to one another, and you can keep your sanity.
