Time Functions

strftime


#include <time.h>
size_t strftime( char *strDest, size_t maxsize,
                 const char *format, const struct tm *timeptr );

Format codes

%a	Abbreviated weekday name
%A	Full weekday name
%b	Abbreviated month name
%B	Full month name
%c	Date and time representation appropriate for locale
%d	Day of month as decimal number (01 - 31)
%H	Hour in 24-hour format (00 - 23)
%I	Hour in 12-hour format (01 - 12)
%j	Day of year as decimal number (001 - 366)
%m	Month as decimal number (01 - 12)
%M	Minute as decimal number (00 - 59)
%p	Current locale’s A.M./P.M. indicator for 12-hour clock
%S	Second as decimal number (00 - 59)
%U	Week of year as decimal number, with Sunday as first day of week (00 - 53)
%w	Weekday as decimal number (0 - 6; Sunday is 0)
%W	Week of year as decimal number, with Monday as first day of week (00 - 53)
%x	Date representation for current locale
%X	Time representation for current locale
%y	Year without century, as decimal number (00 - 99)
%Y	Year with century, as decimal number
%z, %Z	Time-zone name or abbreviation; no characters if time zone is unknown
%%	Percent sign

Sample Code

The following sample code is taken from the Microsoft Visual Studio documentation.

/* TIMES.C illustrates various time and date functions including:
 *      time            _ftime          ctime       asctime
 *      localtime       gmtime          mktime      _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>

void main()
{
    char tmpbuf[128], ampm[] = "AM";
    time_t ltime;
    struct _timeb 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. */
    time( &ltime );
    printf( "Time in seconds since UTC 1/1/70:\t%ld\n", ltime );
    printf( "UNIX time and date:\t\t\t%s", ctime( &ltime ) );

    /* Display UTC. */
    gmt = gmtime( &ltime );
    printf( "Coordinated universal time:\t\t%s", asctime( gmt ) );

    /* Convert to time structure and adjust for PM if necessary. */
    today = localtime( &ltime );
    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. */
    _ftime( &tstruct );
    printf( "Plus milliseconds:\t\t\t%u\n", tstruct.millitm );
    printf( "Zone difference in seconds from UTC:\t%u\n", 
             tstruct.timezone );
    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( mktime( &xmas ) != (time_t)-1 )
   printf( "Christmas\t\t\t\t%s\n", asctime( &xmas ) );

    /* Use time structure to build a customized time string. */
    today = localtime( &ltime );

    /* 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 );
}



Output

OS time:                                21:51:03
OS date:                                05/03/94
Time in seconds since UTC 1/1/70:       768027063
UNIX time and date:                     Tue May 03 21:51:03 1994
Coordinated universal time:             Wed May 04 04:51:03 1994
12-hour time:                           09:51:03 PM
Plus milliseconds:                      279
Zone difference in seconds from UTC:    480
Time zone name:                         
Daylight savings:                       YES
Christmas                               Sat Dec 25 12:00:00 1993

Today is Tuesday, day 03 of May in the year 1994.

b r a y d e n . o r g / Software

Time Functions

strftime

Format codes

Sample Code