difftime - calculate time difference

#include <time.h>
double difftime(time_t time1, time_t time0);

The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double. Each time is a count of seconds.

difftime(b, a) acts like (b-a) except that the result does not overflow and is rounded to double.

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