Timespec relativity?

[spice knoll]

Suppose I call timespec_get(whatever, TIME_UTC) on my laptop, fly an incredibly fast aircraft around the Earth with the laptop beside me, and then call timespec_get again and compute the difference. Am I getting the time that passed for me, or the time that passed on Earth?

[shy ravine]

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[verbal wolf]

For you.

The laptop is moving with you.

[undone slate]

a modern computer connected to the internet will probably use time servers to keep in sync with earth time

otherwise it will probably just use the internal clock

the standard only says "the number of seconds since an implementation defined epoch" so the reference frame is implementation defined

[spice knoll]

I see. Really interesting

[spice knoll]

C23 also defines optional TIME_[THREAD_]ACTIVE to replace clock()

Those should unequivocally measure active processing time

[undone slate]

they measure "the implementation's best approximation" of processing time

most computers have internal clocks but in principle a computer could use an external clock to estimate time elapsed

[spice knoll]

Yeah, that makes sense