linux man page for difftime

DIFFTIME(3)						     Linux Programmer's Manual						       DIFFTIME(3)

NAME
       difftime - calculate time difference

SYNOPSIS
       #include <time.h>

       double difftime(time_t time1, time_t time0);

DESCRIPTION
       The  difftime()	function  returns  the	number of seconds elapsed between time time1 and time time0, represented as a double.  Each of the
       times is specified in calendar time, which means its value is a measurement (in seconds) relative to the Epoch, 1970-01-01  00:00:00  +0000
       (UTC).

CONFORMING TO
       SVr4, 4.3BSD, C89, C99.

NOTES
       On a POSIX system, time_t is an arithmetic type, and one could just define

	      #define difftime(t1,t0) (double)(t1 - t0)

       when the possible overflow in the subtraction is not a concern.	On other systems, the data type time_t might use some other encoding where
       subtraction doesn't work directly.

SEE ALSO
       date(1), gettimeofday(2), time(2), ctime(3), gmtime(3), localtime(3)

COLOPHON
       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2010-02-25							       DIFFTIME(3)