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GETTIMEOFDAY(2) 	       System Calls Manual		 GETTIMEOFDAY(2)

NAME
     gettimeofday, settimeofday -- get/set date and time

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/time.h>

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

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

DESCRIPTION
     Note: The gettimeofday function (but not settimeofday) is obsolescent.  See
     the "STANDARDS" section for more details.

     The system's notion of the current Greenwich time and the current time zone
     is  obtained with the gettimeofday() system call, and set with the settime-
     ofday() system call.  The time is expressed  in  seconds  and  microseconds
     since  midnight  (0  hour),  January 1, 1970.  The resolution of the system
     clock is hardware dependent, and the time may be updated continuously or in
     "ticks".  If tp or tzp is NULL, the associated time information will not be
     returned or set.

     The structures pointed to by tp and tzp are defined in <sys/time.h> as:

     struct timeval {
	     time_t	     tv_sec;	     /* seconds */
	     suseconds_t     tv_usec;	     /* and microseconds */
     };

     struct timezone {
	     int     tz_minuteswest; /* minutes west of Greenwich */
	     int     tz_dsttime;     /* type of dst correction */
     };

     The timezone structure indicates the local time zone (measured  in  minutes
     of  time  westward  from Greenwich), and a flag that, if nonzero, indicates
     that Daylight Saving time applies locally during the  appropriate	part  of
     the  year.   The  kernel generally does not track these values and they are
     usually returned as zero.	Use localtime(3) to find the offset for the cur-
     rently active timezone.

     Only the super-user may set the time of day or time zone.	If the system is
     running at securelevel >= 2 (see init(8)), the time may only be advanced or
     retarded by a maximum of one second.  This limitation is imposed to prevent
     a malicious super-user from setting arbitrary time stamps	on  files.   The
     system  time  can	be adjusted backwards without restriction using the adj-
     time(2) system call even when the system is secure.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the value -1
     is returned and the global variable errno is set to indicate the error.

ERRORS
     The following error codes may be set in errno:

     [EINVAL]		The supplied timeval value is invalid.

     [EPERM]		A user other than the super-user attempted  to	set  the
			time.

SEE ALSO
     date(1), adjtime(2), clock_gettime(2), ctime(3), timeradd(3), clocks(7)

STANDARDS
     The  gettimeofday function is considered obsolescent and its usage discour-
     aged by IEEE Std 1003.1-2008, 2017 Edition (POSIX.1).  Applications  should
     use the clock_gettime(2) function instead.

HISTORY
     The gettimeofday() system call appeared in 4.2BSD.

FreeBSD ports 15.quarterly	 April 28, 2024 		 GETTIMEOFDAY(2)

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