TIME(2) Linux Programmer's Manual TIME(2)
time - get time in seconds
#include <time.h> time_t time(time_t *t);
time() returns the time as the number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). If t is non-NULL, the return value is also stored in the memory pointed to by t.
On success, the value of time in seconds since the Epoch is returned. On error, ((time_t) -1) is returned, and errno is set appropriately.
EFAULT t points outside your accessible address space.
SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX does not specify any error conditions.
POSIX.1 defines seconds since the Epoch using a formula that approximates the number of seconds between a specified time and the Epoch. This formula takes account of the facts that all years that are evenly divisible by 4 are leap years, but years that are evenly divisible by 100 are not leap years unless they are also evenly divisible by 400, in which case they 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 system 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.1-2008 Rationale A.4.15 for further rationale.
date(1), gettimeofday(2), ctime(3), ftime(3), time(7)
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