difftime() - compute difference between two times
#include <time.h>
double difftime (time_t time1, time_t time0)
The difftime(3) function returns the difference between two calendar times, (time1 - time0), expressed in seconds.
External declarations as well as the tm structure definition are in the <time.h> include file.
date(1)
asctime(3)
ctime(3)
gettimeofday(3)
gmtime(3)
getenv(3)
localtime(3)
time(2)