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I don't use Unix time. If someone gives you a Unix time timestamp x, it doesn't mean much unless you check it against a list of leap seconds. By default, your f

by tw1984 3y ago

I don't use Unix time. If someone gives you a Unix time timestamp x, it doesn't mean much unless you check it against a list of leap seconds. By default, your fancy unix time timestamp X doesn't point to a unique second in history, for dozens of times, it pointed to some pretty random 2 seconds intervals. TAI is the only sane choice if you do understand what you are doing. Btw, if you already know that leap second is dead and wondering what happens next, well, they are going to implement leap minute, the good news is you are unlikely to see one in your life time. They are meeting next week to decide on this leap minute proposal. https://www.nytimes.com/2023/11/03/science/time-leap-second.html https://www.nytimes.com/2023/11/03/science/time-leap-second....

ezekiel68 3y ago
And yet... the Sun stubbornly insists on coming up each morning. Therefore, TAI cannot be "the only sane choice" or else the conversion would have happened by now. Either off-by-n leap seconds don't matter enough, or periodically sync'ing with good NTP authorities mitigate it without undue harm. Or ?
- SAI_Peregrinus 3y ago
  Use the time standard that's best suited to your use case. Of course that requires understanding time standards at least a bit. Usually the differences will be minor, but they can matter for things like navigation. Use TAI if you want a monotonic time. UNIX time and GPS time work too, they're fixed offsets from TAI. Use UTC if you want a calendar date/time. Most human interactions are with time zones relative to UTC. Those two cover almost all the cases you'll need. Use UT1 if you want time that roughly tracks the solar time, averaging out the differences in day length due to earth's tilt & elliptical orbit. Use apparent solar time if you really care about calculating where the sun is or will be for some reason and can't just point your solar telescope at it. Use sidereal time if you're trying to calculate where extrasolar objects will be. Use barycentric coordinate time (TCB) if you're plotting the trajectories of interplanetary spacecraft missions or the ephemerides of planets. Various religions have their own time standards used to calculate when holidays occur. There are a few others still usable, even more niche than the above. Use one of the first two and you'll probably be fine.
  - Denvercoder9 3y ago
    Unix time isn't a fixed offset from TAI: it stops the clock during leap seconds (the timestamp for a leap second is the same as for the next second), so the offset from TAI changes at every leap second.

by tw1984 3y ago

ezekiel68 3y ago

And yet... the Sun stubbornly insists on coming up each morning. Therefore, TAI cannot be "the only sane choice" or else the conversion would have happened by now. Either off-by-n leap seconds don't matter enough, or periodically sync'ing with good NTP authorities mitigate it without undue harm. Or ?

SAI_Peregrinus 3y ago
Use the time standard that's best suited to your use case. Of course that requires understanding time standards at least a bit. Usually the differences will be minor, but they can matter for things like navigation. Use TAI if you want a monotonic time. UNIX time and GPS time work too, they're fixed offsets from TAI. Use UTC if you want a calendar date/time. Most human interactions are with time zones relative to UTC. Those two cover almost all the cases you'll need. Use UT1 if you want time that roughly tracks the solar time, averaging out the differences in day length due to earth's tilt & elliptical orbit. Use apparent solar time if you really care about calculating where the sun is or will be for some reason and can't just point your solar telescope at it. Use sidereal time if you're trying to calculate where extrasolar objects will be. Use barycentric coordinate time (TCB) if you're plotting the trajectories of interplanetary spacecraft missions or the ephemerides of planets. Various religions have their own time standards used to calculate when holidays occur. There are a few others still usable, even more niche than the above. Use one of the first two and you'll probably be fine.
- Denvercoder9 3y ago
  Unix time isn't a fixed offset from TAI: it stops the clock during leap seconds (the timestamp for a leap second is the same as for the next second), so the offset from TAI changes at every leap second.