returns the time since the Epoch
(00:00:00 UTC, January 1, 1970), measured in seconds.
the return value is also stored in the memory pointed to by
On success, the value of time in seconds since the Epoch is returned.
On error, ((time_t) -1) is returned, and errno is set
points outside your accessible address space.
SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
POSIX does not specify any error conditions.
seconds since the Epoch
as a value to be interpreted as the number of seconds between a
specified time and the Epoch, according to a formula for conversion
from UTC equivalent to conversion on the naive basis that leap
seconds are ignored and all years divisible by 4 are leap years.
This value is not the same as the actual number of seconds between the time
and the Epoch, because of leap seconds and because clocks are not
required to be synchronized to a standard reference.
The intention is
that the interpretation of seconds since the Epoch values be
consistent; see POSIX.1 Annex B 2.2.2 for further rationale.