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gmtime

Header File

time.h

Category

Time and Date Routines

Prototype

struct tm *gmtime(const time_t *timer);

Description

Converts date and time to Greenwich mean time (GMT).

gmtime accepts the address of a value returned by time and returns a pointer to the structure of type tm containing the time elements. gmtime converts directly to GMT.

The global long variable _timezone should be set to the difference in seconds between GMT and local standard time (in PST _timezone is 8 x 60 x 60). The global variable _daylight should be set to nonzero only if the standard U.S. daylight saving time conversion should be applied.

This is the tm structure declaration from the time.h header file:

struct tm {

int tm_sec; /* Seconds */

int tm_min; /* Minutes */

int tm_hour; /* Hour (0 - 23) */

int tm_mday; /* Day of month (1 - 31) */

int tm_mon; /* Month (0 - 11) */

int tm_year; /* Year (calendar year minus 1900) */

int tm_wday; /* Weekday (0 - 6; Sunday is 0) */

int tm_yday; /* Day of year (0 -365) */

int tm_isdst; /* Nonzero if daylight saving time is in effect. */

};

These quantities give the time on a 24-hour clock, day of month (1 to 31), month (0 to 11), weekday (Sunday equals 0), year - 1900, day of year (0 to 365), and a flag that is nonzero if daylight saving time is in effect.

Return Value

gmtime returns a pointer to the structure containing the time elements. This structure is a static that is overwritten with each call.

Example

Copy Code

    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    /* Pacific Standard Time & Daylight Savings */
    char *tzstr = "TZ=PST8PDT";
    int main(void)
    {
       time_t t;
       struct tm *gmt, *area;
       putenv(tzstr);
       tzset();
       t = time(NULL);
       area = localtime(&t);
       printf("Local time is: %s", asctime(area));
       gmt = gmtime(&t);
       printf("GMT is:        %s", asctime(gmt));
       return 0;
    }

Portability

POSIX | Win32 | ANSI C | ANSI C++
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