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This section describes the time_t data type for representing
calendar time, and the functions which operate on calendar time objects.
These facilities are declared in the header file `time.h'.
This is the data type used to represent calendar time. In the GNU C
library and other POSIX-compliant implementations, time_t is
equivalent to long int. When interpreted as an absolute time
value, it represents the number of seconds elapsed since 00:00:00 on
January 1, 1970, Coordinated Universal Time. (This date is sometimes
referred to as the epoch.)
In other systems, time_t might be either an integer or
floating-point type.
Function: double difftime (time_t time1, time_t time0)
The difftime function returns the number of seconds elapsed
between time time1 and time time0, as a value of type
double.
In the GNU system, you can simply subtract time_t values. But on
other systems, the time_t data type might use some other encoding
where subtraction doesn't work directly.
Function: time_t time (time_t *result)
The time function returns the current time as a value of type
time_t. If the argument result is not a null pointer, the
time value is also stored in *result. If the calendar
time is not available, the value (time_t)(-1) is returned.
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