ultrix man page for adjtime

adjtime(2)							System Calls Manual							adjtime(2)

Name
       adjtime - correct the time to allow synchronization of the system clock

Syntax
       #include <sys/time.h>

       adjtime(delta, olddelta)
       struct timeval *delta;
       struct timeval *olddelta;

Description
       The  system  call  changes the system time, as returned by moving it backward or forward by the number of microseconds corresponding to the
       timeval delta.

       The time is maintained by incrementing it with a machine-dependent tick every clock interrupt.  If delta is negative, the clock	is  slowed
       down  by  incrementing  it  in smaller ticks until the correction is made.  If delta is positive, a larger tick is used.  Thus, the time is
       always a monotonically increasing function.  A time correction from an earlier call to may not be finished when is called again.   If  old-
       delta  is  nonzero, then the structure pointed to will contain, upon return, the number of microseconds still to be corrected from the ear-
       lier call.

       This call can be used in time servers that synchronize the clocks of computers in a local area network.	Such time servers would slow  down
       the clocks of some machines and speed up the clocks of others to bring them to the average network time.

       The call is restricted to the superuser.

Note
       Time is incremented in 3906-microsecond (us) ticks on RISC and 10000 us ticks on VAX.  When is called with a delta less than 1 second, time
       is incremented according to the following table until the time is corrected:

       -------------------------------------------
		Default     Fast	Slow
       System	Increment   Increment	Increment
       -------------------------------------------
       RISC	3906 us     3921 us	3891 us
       VAX	10000 us    10001 us	9999 us
       -------------------------------------------

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

Diagnostics
       The following error codes may be set in errno:

       [EFAULT]       An argument points outside the process's allocated address space.

       [EPERM]	      The process's effective user ID is not that of the super-user.

See Also
       date(1), gettimeofday(2)

																	adjtime(2)