gmtime
Remonter à Time.h - Index
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
#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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