Really the idea that there will enough civilizational continuity that our current timekeeping infrastructure and systems will continue unbroken for that long is insane.
We’re still using a calendar developed over 400 years ago and just making minor tweaks. Without some central global authority, change is unlikely. And even with that, it would be extraordinary disruptive.
The middle for the day, on our time keeping devices, being light outside goes all the way back to the first sundials over 3,000 years ago.
Small and regular maintenance is more realistic than expecting a complete overhaul of timekeeping at some point when are lack of maintenance becomes so problematic that the whole system needs to be thrown away.
Most of the world is perfectly fine with 12:00 not being synchronized with high noon [0]. And some jurisdictions still semiannually f*k with it further using DST. Generously assuming the current time keeping system will survive for ~6k years (looking at the leap seconds accumulation rate for the last 50 years) we can just shift timezones by one hour.
[0]: https://64.media.tumblr.com/4a9a4613f057d3b5f17ec548e6ac06d1...
Do you know how long that is on a civilizational scale? When we try to develop warnings for nuclear waste storage that will last that long it’s mostly impossible because we assume there will be absolutely no civilizational continuity/shared context.
Doing 20k years of regular maintenance just in case we somehow keep using the same timekeeping system is completely unhinged. Better to jump an hour in 6k years if people in 6k years decide they care.
6,000 years ago is 1,000 years before Stonehenge.
And this isn’t about whether we use the same calendar, we’re talking about whether we have time keeping continuity down to the second. This requires infrastructure continuity and essentially no adjustments whatsoever over that time.