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.)