Time Management

Use these functions to get the current time and convert, adjust, and store it as necessary. The current time is the system time.

The _ftime and localtime routines use the TZ environment variable. If TZ is not set, the run-time library attempts to use the time-zone information specified by the operating system. If this information is unavailable, these functions use the default value of PST8PDT. For more information on TZ, see _tzset; also see _daylight, timezone, and _tzname.

Time Routines

Function	Use
asctime, _wasctime	Convert time from type structtm to character string
clock	Return elapsed CPU time for process
ctime, _wctime	Convert time from type time_t to character string
difftime	Compute difference between two times
_ftime	Store current system time in variable of type struct _timeb
_futime	Set modification time on open file
gmtime	Convert time from type time_t to struct tm
localtime	Convert time from type time_t to struct tm with local correction
mktime	Convert time to calendar value
_strdate, _wstrdate	Return current system date as string
strftime, wcsftime	Format date-and-time string for international use
_strtime, _wstrtime	Return current system time as string
time	Get current system time as type time_t
_tzset	Set external time variables from environment time variable TZ
_utime, _wutime	Set modification time for specified file using either current time or time value stored in structure

Note   In all versions of Microsoft C/C++ except Microsoft C/C++ version 7.0, and in all versions of Microsoft Visual C++, the time function returns the current time as the number of seconds elapsed since midnight on January 1, 1970. In Microsoft C/C++ version 7.0, time returned the current time as the number of seconds elapsed since midnight on December 31, 1899.