By then, I don’t think that the use of earth’s orbital period around the sun would make sense as a unit of measurement. It is important to track the seasons if you’re living in an agricultural society. But the orbital period of the earth is not consistent across time, nor the time it takes for the earth to rotate. It doesn’t make a good unit of measurement. And don’t get me started on leap years, leap seconds, negative leap seconds, timezones and daylight saving times…

I’d prefer to base the new unit of time based on “Plank time”. About 10^44 of these are about one second. Now if we switch to the duodecimal system we can define 12^41 × Plank time to be our standard unit. It’s about a third of an earth second. 144 of these (12^43) equal roughly 3/4 of a minute. 144 of these (12^45) is about 1.8 hours. 12 of these (12^46) could be the equivalent of a day, 12 of that could be an equivalent of a week, and you can find an equivalent for a year. The duodecimal is unnecessary, but it makes division a bit neater. Now peak a date well before the beginning of human history to avoid the need for negative years (BC / AD) and that’s it.

That way you get a single number that you can manipulate arithmetically. Not like yyyy/mm/dd format where each part is a different length.