settimeofday()--Set System Clock

 #include <sys/time.h>

 int settimeofday (struct timeval *tp,
                  struct timezone *tzp);

  Service Program Name: QWCTZUTC

  Default Public Authority: *USE

  Threadsafe: Yes

The settimeofday() function sets the system clock to the Coordinated Universal Time (UTC) contained in the timeval structure pointed to by tp. The tzp parameter is not used.


(Input) A pointer to a timeval structure that contains the time in seconds and microseconds since 1 January 1970, 00:00:00 UTC (epoch-1970).

This parameter is not used.

Authorities and Locks

Special Authority

Return Value

Error Conditions

If settimeofday() is not successful, errno usually indicates one of the following errors. Under some conditions, errno could indicate an error other than those listed here.

Error Messages


Related Information


The following example sets the system clock.

Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.

#include <sys/time.h>
#include <stdio.h>
#include <errno.h>

int main(int argc, char *argv[])
    struct timeval now;
    int rc;


    rc=settimeofday(&now, NULL);
    if(rc==0) {
        printf("settimeofday() successful.\n");
    else {
        printf("settimeofday() failed, "
        "errno = %d\n",errno);
        return -1;

    return 0;
Example Output:
settimeofday() successful.

API introduced: V4R2

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