Time.

Routine Use
asctime
Convert from struct tm to a character string
clock
Return the cpu time used by the current program
ctime
Convert from time_t to a character string
difftime
Calculate the difference between two times
gettimeofday
Gets the current time and timezone information
gmtime
Convert from time_t to struct tm
localtime
Convert from time_t to struct tm in the local timezone
mktime
Convert from struct tm to time_t
strftime
Format a date and/or time string
time
Gets the current time as a time_t