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+.\" Copyright (c) 1980, 1991, 1993
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)adjtime.2	8.1 (Berkeley) 6/4/93
+.\"
+.Dd June 4, 1993
+.Dt ADJTIME 2
+.Os BSD 4.3
+.Sh NAME
+.Nm adjtime
+.Nd "correct the time to allow synchronization of the system clock"
+.Sh SYNOPSIS
+.Fd #include <sys/time.h>
+.Ft int
+.Fn adjtime "struct timeval *delta" "struct timeval *olddelta"
+.Sh DESCRIPTION
+.Fn Adjtime
+makes small adjustments to the system time, as returned by
+.Xr gettimeofday 2 ,
+advancing or retarding it
+by the time specified by the timeval
+.Fa delta .
+If
+.Fa delta
+is negative, the clock is
+slowed down by incrementing it more slowly than normal until
+the correction is complete.
+If
+.Fa delta
+is positive, a larger increment than normal
+is used.
+The skew used to perform the correction is generally a fraction of one percent.
+Thus, the time is always
+a monotonically increasing function.
+A time correction from an earlier call to
+.Fn adjtime
+may not be finished when
+.Fn adjtime
+is called again.
+If
+.Fa olddelta
+is non-nil,
+the structure pointed to will contain, upon return, the
+number of microseconds still to be corrected
+from the earlier call.
+.Pp
+This call may be used by 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.
+.Pp
+The call 
+.Fn adjtime
+is restricted to the super-user.
+.Sh 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
+.Va errno .
+.Sh ERRORS
+.Fn Adjtime
+will fail if:
+.Bl -tag -width Er
+.It Bq Er EFAULT
+An argument points outside the process's allocated address space.
+.It Bq Er EPERM
+The process's effective user ID is not that of the super-user.
+.El
+.Sh SEE ALSO
+.Xr date 1 ,
+.Xr gettimeofday 2 ,
+.Xr timed 8 ,
+.Xr timedc 8 ,
+.Rs
+.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
+.%A R. Gusella
+.%A S. Zatti
+.Re
+.Sh HISTORY
+The
+.Nm
+function call appeared in
+.Bx 4.3 .