Comment by photochemsyn

Computerphile has a really amusing (sort of) video on the related issue of how to translate between internet time and local time zones (though they have a different opinion about the wisdom of 'leap smears' vs 'leap seconds'):

https://www.youtube.com/watch?v=-5wpm-gesOY

Note that the common-sense notion that time intervals are fixed fails when relativistic concepts are introduced. Atomic clocks get out of sync due to being in different relativistic frames (satellites vs. ground, for example). Hence designating a 'universal time' is always going to be somewhat arbitrary.

https://blog.swiftnav.com/relativistic-correction/