And we are worried about a few seconds off.........

[Mike on a bike]

https://www.realclearscience.com/articles/2018/10/27/why_we_will_probably_never_have_a_perfect_clock_110780.html

[Nanuq]

Oh it gets much worse Mike! In a universe with isotropic gravitational fields your examples are true. But surrounded as we are by huge gravitational masses we pull back the covers to reveal the realm of relative time. Et voila'



And now things get very weird indeed. Inertial mass and gravitational mass are indistinguishable and no accelerated reference frames agree. In a nutshell clocks near large masses run more quickly because gravitational time dilation appears as accelerated frames of reference. And bingo zingo, clocks run at different rates.

Which explains why you and me are always setting our watches back I suppose!

[Sogeha]

Not to mention that time is a function of heat anyway. No heat as in no particle movement and no time. This is way the commonly asked question of what came before the Big Bang is a bit illogical. Essentially there was no time, so there was no before, at least not in this universe. So as the universe cools, we can expect time to slow down, which is really going to mess with all those fancy perpetual calendars