time_t

Run-Time Library Reference

time, _time64

Get the system time.time_t time(
time_t *timer
);
__time64_t _time64(
__time64_t *timer
);

Parameters

timer
Pointer to the storage location for time.

Return Value

Return the time in elapsed seconds. There is no error return.

A call to time or _time64 can fail, however, if the date passed to the function is:

Before midnight, January 1, 1970.

After 19:14:07, January 18, 2038, UTC (using time and time_t).

After 23:59:59, December 31, 3000, UTC (using _time64 and __time64_t).

Remarks

The time function returns the number of seconds elapsed since midnight (00:00:00), January 1, 1970, coordinated universal time (UTC), according to the system clock. The return value is stored in the location given by timer. This parameter may be NULL, in which case the return value is not stored.

Requirements

Routine	Required header	Compatibility
time	<time.h>	ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP
_time64	<time.h>	Win 98, Win Me, Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.

Libraries
All versions of the C run-time libraries.

Example

// crt_times.c
/* This program demonstrates these time and date functions:
*      _time64         _ftime64        _ctime64     asctime
*      _localtime64    _gmtime64       _mktime64    _tzset
*      _strtime        _strdate        strftime
*
* Also the global variable:
*      _tzname
*/

#include <time.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/timeb.h>
#include <string.h>

int main()
{
char tmpbuf[128], ampm[] = "AM";
__time64_t ltime;
struct __timeb64 tstruct;
struct tm *today, *gmt, xmas = { 0, 0, 12, 25, 11, 93 };

/* Set time zone from TZ environment variable. If TZ is not set,
* the operating system is queried to obtain the default value
* for the variable.
*/
_tzset();

/* Display operating system-style date and time. */
_strtime( tmpbuf );
printf( "OS time:/t/t/t/t%s/n", tmpbuf );
_strdate( tmpbuf );
printf( "OS date:/t/t/t/t%s/n", tmpbuf );

/* Get UNIX-style time and display as number and string. */
_time64( <ime );
printf( "Time in seconds since UTC 1/1/70:/t%ld/n", ltime );
printf( "UNIX time and date:/t/t/t%s", _ctime64( <ime ) );

/* Display UTC. */
gmt = _gmtime64( <ime );
printf( "Coordinated universal time:/t/t%s", asctime( gmt ) );

/* Convert to time structure and adjust for PM if necessary. */
today = _localtime64( <ime );
if( today->tm_hour >= 12 )
{
strcpy( ampm, "PM" );
today->tm_hour -= 12;
}
if( today->tm_hour == 0 )  /* Adjust if midnight hour. */
today->tm_hour = 12;

/* Note how pointer addition is used to skip the first 11
* characters and printf is used to trim off terminating
* characters.
*/
printf( "12-hour time:/t/t/t/t%.8s %s/n",
asctime( today ) + 11, ampm );

/* Print additional time information. */
_ftime64( &tstruct );
printf( "Plus milliseconds:/t/t/t%u/n", tstruct.millitm );
printf( "Zone difference in hours from UTC:/t%u/n",
tstruct.timezone/60 );
printf( "Time zone name:/t/t/t/t%s/n", _tzname[0] );
printf( "Daylight savings:/t/t/t%s/n",
tstruct.dstflag ? "YES" : "NO" );

/* Make time for noon on Christmas, 1993. */
if( _mktime64( &xmas ) != (__time64_t)-1 )
printf( "Christmas/t/t/t/t%s/n", asctime( &xmas ) );

/* Use time structure to build a customized time string. */
today = _localtime64( <ime );

/* Use strftime to build a customized time string. */
strftime( tmpbuf, 128,
"Today is %A, day %d of %B in the year %Y./n", today );
printf( tmpbuf );
}

Sample Output

OS time:                                14:15:49
OS date:                                02/07/02
Time in seconds since UTC 1/1/70:       1013120149
UNIX time and date:                     Thu Feb 07 14:15:49 2002
Coordinated universal time:             Thu Feb 07 22:15:49 2002
12-hour time:                           02:15:49 PM
Plus milliseconds:                      455
Zone difference in hours from UTC:      8
Time zone name:                         Pacific Standard Time
Daylight savings:                       NO
Christmas                               Sat Dec 25 12:00:00 1993

Today is Thursday, day 07 of February in the year 2002.