March is already summer here (Southern Hemisphere). We have all sorts of weird eccentricities due to "cultural norms" (we use snowflakes on our Christmas cards in mid-summer, whereas the Steam Summer Sale happens mid-winter).

Not to mention with climate change, we're probably going to have to deal with many other changes in season etc. anyway.

All of us deal with the fact that the day gets shorter and longer every year anyway (and daylight savings didn't seem to be a terribly good solution).

I think having the seasons slowly drift is a non-issue, provided it's just slow enough to not be noticeable from year to year.

Yeah, I can see that being an issue, at least until a decent proportion of humanity lives off-world. I can't see people living in the asteroid belts adding arbitrary leap-seconds.

Of course, once you start dealing with astronomical distances and speeds, the whole concept of a single universal measure of time kind of goes out the window anyway so it's probably going to get worse, not better. :P

(FWIW my definition of 'best' here is something along the lines of 'simple, no special rules or tinkering, gets translated to a human-readable local time on demand'. Which is pretty much how Unix epoch works, come to think of it.)

Yes... let's let future asteroid dwellers solve their own problems, which will be as much cultural as technical. Today's elegant universal solution is sometimes tomorrow's Esperanto: perfectly useless.