The system's notion of the current Greenwich time is obtained with the gettimeofday() call, and set with the settimeofday() call. The current time is expressed in elapsed seconds and microseconds since 00:00 GMT, January 1, 1970 (zero hour). The resolution of the system clock is hardware dependent; the time may be updated continuously, or in clock ticks.

long tv_sec; /* seconds since Jan. 1, 1970 */ long tv_usec; /* and microseconds */

tp points to a timeval structure, which includes the following members:

If tp is a NULL pointer, the current time information is not returned or set.

tzp is an obsolete pointer formerly used to get and set timezone information. tzp is now ignored. Timezone information is now handled using the TZ environment variable; see TIMEZONE(4).

Only the privileged user may set the time of day.

A -1 return value indicates an error occurred; in this case an error code is stored in the global variable errno.

The following error codes may be set in errno:

EINVAL

tp specifies an invalid time.

EPERM

A user other than the privileged user attempted to set the time.

adjtime(2), ctime(3C), gettimeofday(3C), TIMEZONE(4)

Use of these interfaces should be restricted to only applications written on BSD platforms. Use of these interfaces with any of the system libraries or in multi-thread applications is unsupported.

tzp is ignored in SunOS 5.X releases.

tv_usec is always 0.