Convert time_t from localtime zone to UTC

Question

I have a time_t that represents the time in seconds since epoch. Those seconds refer to the local time.

I want to convert them to UTC.

Is there

Answer 1

If you are okay with using Abseil's time library, one other way to do this is:

auto civil_second =
  absl::LocalTimeZone().At(absl::FromTimeT()).cs;

time_t time_in_utc = absl::ToTimeT(absl::FromCivil(civil_second, absl::UTCTimeZone()));

(Maybe there is a simpler set of calls in the library to do this, but I have not explored further. :))