[dotancohen]

You have the same problem in Gregorian calendar, no?

How many leap seconds will occur between now and when Europa Clipper intercepts Jupiter? That's actually important to know, e.g. for scheduling radio telescope time.

And let's not forget that some Pacific island nations have actually skipped entire days to just to another side of the date line.

[Martinussen]

That's what the end of my last comment was trying to touch on - timestamps are always imperfect for certain edge cases, but I would say that scheduling radio telescope time probably doesn't meaningfully benefit from trying to latch itself on to this RFC either, in that case?

The problem of "All future dates beyond the current year are currently unknown" is unsolvable in a very different way to "cultures and systems might change in the future".

(Though, wouldn't you be fine in your example? "X time after TS" wouldn't change, right? If you need atomic time anyways.)

[dotancohen]

The culture is not changing. They just don't know on what specific day they will be able to observe the moon some months.

[Martinussen]

I meant that "Cultures and systems might change in the future" is the current/proposed state, and "All future dates beyond the current year are currently unknown" is unreasonable.