NAME
gettimeofday, settimeofday - get/set date and time

SYNOPSIS
#include <sys/time.h>

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

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

DESCRIPTION
The system’s notion of the current Greenwich time and the current
time zone is obtained with the gettimeofday call, and set with the
settimeofday 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 {
long tv_sec; /* seconds since Jan. 1, 1970 */
long tv_usec; /* and microseconds */
};

struct timezone {
int tz_minuteswest; /* of Greenwich */
int tz_dsttime; /* type of dst correction to apply */
};

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.

Only the super-user may set the time of day or time zone.

RETURN
A 0 return value indicates that the call succeeded. A -1 return
value indicates an error occurred, and in this case an error code
is stored into the global variable errno.

ERRORS
The following error codes may be set in errno:

[EFAULT] An argument address referenced invalid memory.

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

SEE ALSO
date(1), adjtime(2), ctime(3)