path: root/bin/date/date.1

.\"	$OpenBSD: date.1,v 1.45 2006/01/08 00:19:55 jmc Exp $
.\"	$NetBSD: date.1,v 1.12 1996/03/12 04:32:37 phil Exp $
.\"
.\" Copyright (c) 1980, 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" 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. 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.
.\"
.\"     @(#)date.1	8.3 (Berkeley) 4/28/95
.\"
.Dd April 28, 1995
.Dt DATE 1
.Os
.Sh NAME
.Nm date
.Nd display or set date and time
.Sh SYNOPSIS
.Nm date
.Op Fl ajnu
.Op Fl d Ar dst
.Op Fl r Ar seconds
.Op Fl t Ar minutes_west
.Op Cm + Ns Ar format
.Sm off
.Oo Oo Oo Oo Oo Oo
.Ar cc Oc
.Ar yy Oc
.Ar mm Oc
.Ar dd Oc
.Ar HH Oc
.Ar MM Op Ar \&.SS Oc
.Sm on
.Sh DESCRIPTION
When invoked without arguments, the
.Nm
utility displays the current date and time.
Otherwise, depending on the options specified,
.Nm
will set the date and time or print it in a user-defined way.
.Pp
Only the superuser may set the date.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl a
Use the
.Xr adjtime 2
call to gradually skew the local time to the
remote time rather than just hopping.
.It Fl d Ar dst
Set the system's value for Daylight Saving Time.
If
.Ar dst
is non-zero, future calls
to
.Xr gettimeofday 2
will return a non-zero value for
.Fa tz_dsttime .
.It Fl j
Parse the provided date and time and display the result without changing
the clock.
.It Fl n
By default,
if the
.Xr timed 8
daemon is running,
.Nm
sets the time on all of the machines in the local group.
The
.Fl n
option suppresses this behavior and causes the time to be set only on the
current machine.
.It Fl r Ar seconds
Print out (in specified format) the date and time represented by
.Ar seconds
from the Epoch.
.It Fl t Ar minutes_west
Set the system's value for minutes west of
.Tn GMT .
.Ar minutes_west
specifies the number of minutes returned in
.Fa tz_minuteswest
by future calls to
.Xr gettimeofday 2 .
.It Fl u
Display or set the date in UTC (Coordinated Universal) time.
.El
.Pp
An operand with a leading plus sign
.Pq Sq +
signals a user-defined format
string which specifies the format in which to display the date and time.
The format string may contain any of the conversion specifications described
in the
.Xr strftime 3
manual page, as well as any arbitrary text.
A newline
.Pq Ql \en
character is always output after the characters specified by
the format string.
The format string for the default display is:
.Bd -literal -offset indent
%a %b %e %H:%M:%S %Z %Y
.Ed
.Pp
If an operand does not have a leading plus sign, it is interpreted as
a value for setting the system's notion of the current date and time.
The canonical representation for setting the date and time is:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ar ccyy
Year:
the first two digits (representing the century) may be omitted
for non-ambiguous years (1969\-2068).
.It Ar mm
Numeric month: a number from 1 to 12.
.It Ar dd
Day: a number from 1 to 31.
.It Ar HH
Hour: a number from 0 to 23.
.It Ar MM
Minute: a number from 0 to 59.
.It Ar SS
Second: a number from 0 to 61 (59 plus a maximum of two leap seconds).
.El
.Pp
Everything but the minute is optional.
.Pp
Time changes for Daylight Saving Time, standard time, leap seconds,
and leap years are handled automatically.
.Sh ENVIRONMENT
.Bl -tag -width Ds
.It Ev TZ
The time zone to use when displaying dates.
See
.Xr environ 7
for more information.
If this variable is not set, the time zone is determined based on
.Pa /etc/localtime ,
which the administrator adjusts using
the
.Fl l
option of
.Xr zic 8 .
.El
.Sh FILES
.Bl -tag -width /var/log/messages -compact
.It Pa /var/log/wtmp
record of date resets and time changes
.It Pa /var/log/messages
record of the user setting the time
.El
.Sh EXAMPLES
Display the date using the specified format string:
.Bd -literal -offset indent
$ date "+DATE: %Y-%m-%d%nTIME: %H:%M:%S"
DATE: 1987-11-21
TIME: 13:36:16
.Ed
.Pp
Set the date to
June 13, 1985, 4:27 PM:
.Pp
.Dl # date 8506131627
.Pp
Set the time to
2:32 PM,
without modifying the date:
.Pp
.Dl # date 1432
.Sh DIAGNOSTICS
Exit status is 0 on success, 1 if unable to set the date, and 2
if able to set the local date, but unable to set it globally.
.Pp
Occasionally, when
.Xr timed 8
synchronizes the time on many hosts, the setting of a new time value may
require more than a few seconds.
On these occasions,
.Nm
prints:
.Dq Network time being set .
The message
.Dq Communication error with timed
occurs when the communication
between
.Nm
and
.Xr timed 8
fails.
.Sh SEE ALSO
.Xr adjtime 2 ,
.Xr gettimeofday 2 ,
.Xr strftime 3 ,
.Xr utmp 5 ,
.Xr ntpd 8 ,
.Xr rdate 8 ,
.Xr timed 8
.Rs
.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
.%A R. Gusella
.%A S. Zatti
.Re
.Sh STANDARDS
The
.Nm
utility is expected to be compatible with
.St -p1003.2 .
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .