I would argue that all machines, on Earth or otherwise, should run on UTC! Only when interacting with a human should the output be converted to the local time of that human.

UTC

Good question as time is slower in space..

Time is slower (relative to us) due to spacecraft being in motion (relative to us).

But then time is faster (relative to us) because it is higher up in the gravity well.

https://www.telegraph.co.uk/news/science/science-news/802098...

So which one wins out?

Interestingly, it depends on your altitude. For objects in a low, fast orbit such as the ISS, time runs slower; in higher, slower orbits, such as GPS and geostationary communications satellites, time runs faster. In between these points, the effects cancel out at an altitude of roughly 3000km.

https://en.wikipedia.org/wiki/Time_dilation#/media/File:Time...

However, both effects can be ignored for almost all purposes. The effect of time dilation is less than 1 part per billion, which is basically undetectable without an atomic clock.

Yes, especially because clock drift on the crystals is several orders of magnitude higher. Often 10 parts per million, or more.