date()

Print or/and set the date 

settimeoftheday()

System call to set the time of the day 

gettimeoftheday()

System call to get the time of the day 

adjtime()

System call to adjust the time of the day smoothly (used by the Network Time Protocol, NTP) 

ctime()

Returns time argument as local time in ASCII string 

localtime()

Returns time argument as local time in a structure 

gmtime()

Returns time argument without local adjustment 

asctime()

Returns ASCII time from time structure argument 

mktime()

Returns time value from time structure argument 

strftime()

Format printf like time from structure argument 

tzset()

Set time zone information for time conversion routines