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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 3.35 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.