247 lines
6.3 KiB
Groff
247 lines
6.3 KiB
Groff
.\" $NetBSD: date.1,v 1.42 2012/04/06 11:36:56 wiz Exp $
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.\"
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.\" Copyright (c) 1980, 1990, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)date.1 8.3 (Berkeley) 4/28/95
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.\"
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.Dd November 15, 2006
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.Dt DATE 1
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.Os
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.Sh NAME
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.Nm date
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.Nd display or set date and time
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.Sh SYNOPSIS
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.Nm
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.Op Fl ajnu
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.Op Fl d Ar date
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.Op Fl r Ar seconds
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.Op Cm + Ns Ar format
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.Sm off
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.Oo Oo Oo Oo Oo Oo
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.Ar CC Oc
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.Ar yy Oc
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.Ar mm Oc
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.Ar dd Oc
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.Ar HH Oc Ar MM Oo
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.Li \&. Ar SS Oc Oc
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.Sm on
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.Sh DESCRIPTION
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.Nm
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displays the current date and time when invoked without arguments.
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Providing arguments will format the date and time in a user-defined
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way or set the date.
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Only the superuser may set the date.
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl a
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Use
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.Xr adjtime 2
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to change the local system time slowly,
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maintaining it as a monotonically increasing function.
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.Fl a
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implies
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.Fl n .
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.It Fl d Ar date
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Parse the provided human-described date and time and display the result without
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actually changing the system clock.
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(See
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.Xr parsedate 3
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for examples.)
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.It Fl j
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Parse the provided canonical representation of date and time (described below)
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and display the result without actually changing the system clock.
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.It Fl n
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The utility
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.Xr timed 8
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is used to synchronize the clocks on groups of machines.
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By default, if
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.Xr timed 8
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is running,
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.Nm
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will set the time on all of the machines in the local group.
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The
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.Fl n
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option stops
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.Nm
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from setting the time for other than the current machine.
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.It Fl r Ar seconds
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Print out the date and time that is
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.Ar seconds
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from the Epoch.
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.It Fl u
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Display or set the date in
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.Tn UTC
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(universal) time.
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.El
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.Pp
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An operand with a leading plus
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.Pq Cm +
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sign signals a user-defined format
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string which specifies the format in which to display the date and time.
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The format string may contain any of the conversion specifications described
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in the
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.Xr strftime 3
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manual page, as well as any arbitrary text.
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A \*[Lt]newline\*[Gt] character is always output after the characters
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specified by the format string.
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The format string for the default display is:
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.Bd -literal -offset indent
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%a %b %e %H:%M:%S %Z %Y
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.Ed
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.Pp
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If an operand does not have a leading plus sign, it is interpreted as
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a value for setting the system's notion of the current date and time.
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The canonical representation for setting the date and time is:
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.Pp
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.Bl -tag -width Ds -compact -offset indent
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.It Ar CC
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The first two digits of the year (the century).
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.It Ar yy
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The second two digits of the year.
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If
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.Ar yy
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is specified, but
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.Ar CC
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is not, a value for
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.Ar yy
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between 69 and 99 results in a
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.Ar CC
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value of 19.
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Otherwise, a
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.Ar CC
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value of 20 is used.
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.It Ar mm
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The month of the year, from 01 to 12.
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.It Ar dd
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The day of the month, from 01 to 31.
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.It Ar HH
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The hour of the day, from 00 to 23.
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.It Ar MM
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The minute of the hour, from 00 to 59.
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.It Ar SS
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The second of the minute, from 00 to 61.
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.El
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.Pp
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Everything but the minutes is optional.
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.Pp
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Time changes for Daylight Saving and Standard Time and leap seconds
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and years are handled automatically.
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.Sh ENVIRONMENT
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The following environment variables affect the execution of
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.Nm :
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.Bl -tag -width iTZ
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.It Ev TZ
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The timezone to use when displaying dates.
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See
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.Xr environ 7
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for more information.
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.El
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.Sh FILES
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.Bl -tag -width /var/log/messages -compact
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.It Pa /etc/localtime
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Symlink pointing to system's default timezone information file in
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.Pa /usr/share/zoneinfo
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directory.
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.It Pa /var/log/wtmp
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A record of date resets and time changes.
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.It Pa /var/log/messages
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A record of the user setting the time.
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.El
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.Sh EXAMPLES
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The command:
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.Bd -literal -offset indent
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date '+DATE: %m/%d/%y%nTIME: %H:%M:%S'
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.Ed
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.Pp
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will display:
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.Bd -literal -offset indent
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DATE: 11/21/87
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TIME: 13:36:16
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.Ed
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.Pp
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The command:
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.Bd -literal -offset indent
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date 8506131627
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.Ed
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.Pp
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sets the date to
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.Dq Li "June 13, 1985, 4:27 PM" .
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.Pp
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The command:
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.Bd -literal -offset indent
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date 1432
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.Ed
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.Pp
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sets the time to
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.Li "2:32 PM" ,
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without modifying the date.
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.Sh DIAGNOSTICS
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Exit status is 0 on success, 1 if unable to set the date, and 2
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if able to set the local date, but unable to set it globally.
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.Pp
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Occasionally, when
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.Xr timed 8
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synchronizes the time on many hosts, the setting of a new time value may
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require more than a few seconds.
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On these occasions,
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.Nm
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prints:
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.Ql Network time being set .
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The message
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.Ql Communication error with
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.Xr timed 8
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occurs when the communication
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between
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.Nm
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and
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.Xr timed 8
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fails.
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.Sh SEE ALSO
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.Xr adjtime 2 ,
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.Xr gettimeofday 2 ,
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.Xr settimeofday 2 ,
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.Xr parsedate 3 ,
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.Xr strftime 3 ,
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.Xr utmp 5 ,
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.Xr environ 7 ,
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.Xr timed 8
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.Rs
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.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
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.%A R. Gusella
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.%A S. Zatti
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.Re
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.Sh STANDARDS
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The
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.Nm
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utility is expected to be compatible with
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.St -p1003.2 .
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