To continue the thought... What about time on different planets? Our time is based on solar revolutions (mostly). If Mars had the same, their time would be different from ours very quickly.
This is already a bit of an issue. GPS satellites have to deliberately run their clocks at the "wrong" rate to cancel out the time dilation caused by their different gravitational potential.
...but if you use UTC, as is standard, it's not exactly "seconds since 1970", as kazagistar claimed (and as you explain in a nearby comment), which was my point.
unixtime is an integer, it has no concept of some seconds being different to other seconds - leap seconds only matter when converting this integer into a "human readable" format :)
> unixtime is an integer, it has no concept of some seconds being different to other seconds - leap seconds only matter when converting this integer into a "human readable" format :)
Except that's not how UNIX timestamps work (incidentally that'd be TAI time, which some non-conformant systems use for UNIX timestamps, and which DJB advocated for a few years ago, issue being TAI isn't really human-friendly).
A UNIX timestamps is UTC, it's defined as 86400 * days since epoch[0] + seconds since midnight[2]. Since UTC takes leap seconds in account, so does a unix timestamp, which in most implementations means a repeated second (and if you have sub-second timestamps, lots of repeated timestamp). Which has lead to the invention of stuff like "leap second smearing" as lots of software doesn't deal well with repeated timestamps, or more generally non-monotonic clocks.
By the by, because UNIX timestamps are now defined based on UTC and UTC didn't exist before January 1st, 1972, timestamps below +63072000 are imprecisely defined and not-entirely-specified approximations of GMT.
I've seen 'sol' used to refer to the period of a solar day on Mars, which is about forty minutes longer than ours here on Earth. You still have to convert, but at least it's clear (ish?) that conversion is required without having to look at the context.
