Using Lua to format 0 seconds as 00:00:00

Question

I'm trying to format a duration (in seconds) as a time and I'm getting results indicating that I'm supposed to account for an epoch somewhere. I expected os.date("%X", 0) to produce "00:00:00" but it is returning "20:00:00" as well as a date value of "12/31/69" (I don't need a calendar date though).

Is there a standard way of getting a time duration string that causes 0 seconds to produce a clock representing a total of zero seconds? I can't seem to find an example anywhere of what I'm trying to do.

Thanks

Answer 1

In most systems (ie, POSIX), os.date("%X",0) gives you the time of the epoch, which is 00:00:00 (Coordinated Universal Time, UTC), 1 January 1970. You get 20:00:00 because you're in a different time zone.

To force UTC instead of your time zone, start the format with !. This is mentioned in the manual.

So, use os.date("!%X",0) to get 00:00:00 as desired. It'll work with any number of seconds less than a day (86400). For instance, os.date("!%X",70) gives 00:01:10: 1 minute and 10 seconds.

Answer 2

Lua does not have a vast standard library:

string.format("%.2d:%.2d:%.2d", s/(60*60), s/60%60, s%60)