249 lines
6.3 KiB
Groff
249 lines
6.3 KiB
Groff
.\" $OpenBSD: date.1,v 1.67 2016/09/12 17:28:47 jca Exp $
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.\" $NetBSD: date.1,v 1.12 1996/03/12 04:32:37 phil 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 $Mdocdate: September 12 2016 $
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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 date
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.Op Fl aju
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.Op Fl d Ar dst
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.Op Fl r Ar seconds
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.Op Fl t Ar minutes_west
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.Op Fl z Ar output_zone
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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
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.Ar MM
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.Op . Ar SS
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.Oc
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.Sm on
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.Sh DESCRIPTION
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When invoked without arguments, the
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.Nm
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utility displays the current date and time.
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Otherwise, depending on the options specified,
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.Nm
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will set the date and time or print it in a user-defined way.
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.Pp
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Changing the system date has some risks, as described in
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.Xr settimeofday 2 .
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Only the superuser may change 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 the
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.Xr adjtime 2
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call to gradually skew the local time to the
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desired time rather than just hopping.
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.It Fl d Ar dst
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Set the system's value for Daylight Saving Time.
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If
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.Ar dst
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is non-zero, future calls
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to
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.Xr gettimeofday 2
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will return a non-zero value for
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.Fa tz_dsttime .
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.It Fl j
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Parse the provided date and time and display the result without changing
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the clock.
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.It Fl r Ar seconds
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Print out (in specified format) the date and time represented by
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.Ar seconds
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from the Epoch.
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.It Fl t Ar minutes_west
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Set the system's value for minutes west of GMT.
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.Ar minutes_west
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specifies the number of minutes returned in
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.Fa tz_minuteswest
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by future calls to
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.Xr gettimeofday 2 .
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.It Fl u
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Display or set the date in UTC (Coordinated Universal) time.
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.It Fl z Ar output_zone
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Just before printing the time, change to the specified timezone;
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see the description of
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.Ev TZ
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below.
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This can be used with
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.Fl j
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to easily convert time specifications from one zone to another.
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.El
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.Pp
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An operand with a leading plus sign
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.Pq Sq +
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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 newline
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.Pq Ql \en
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character is always output after the characters specified by
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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 ccyy
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Year.
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If yy is specified, but cc is not,
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a value for yy between 69 and 99 results in a cc value of 19.
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Otherwise, a cc value of 20 is used.
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.It Ar mm
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Month:
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a number from 1 to 12.
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.It Ar dd
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Day:
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a number from 1 to 31.
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.It Ar HH
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Hour:
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a number from 0 to 23.
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.It Ar MM
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Minute:
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a number from 0 to 59.
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.It Ar SS
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Second:
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a number from 0 to 60
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(permitting a leap second),
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preceded by a period.
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.El
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.Pp
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Everything but the minute is optional.
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.Pp
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Time changes for Daylight Saving Time, standard time, leap seconds,
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and leap years are handled automatically.
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.Sh ENVIRONMENT
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.Bl -tag -width Ds
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.It Ev TZ
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The time zone to use when parsing or 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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If this variable is not set, the time zone is determined based on
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.Pa /etc/localtime ,
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which the administrator adjusts using
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the
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.Fl l
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option of
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.Xr zic 8 .
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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 /var/log/wtmp
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record of date resets and time changes
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.It Pa /var/log/messages
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record of the user setting the time
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.El
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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Display the date using the specified format string:
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.Bd -literal -offset indent
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$ date "+DATE: %Y-%m-%d%nTIME: %H:%M:%S"
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DATE: 1987-11-21
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TIME: 13:36:16
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.Ed
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.Pp
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Set the date to
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June 13, 1985, 4:27 PM:
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.Pp
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.Dl # date 198506131627
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.Pp
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Set the time to
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2:32 PM,
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without modifying the date:
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.Pp
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.Dl # date 1432
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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 strftime 3 ,
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.Xr utmp 5 ,
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.Xr ntpd 8 ,
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.Xr rdate 8
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.Sh STANDARDS
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The
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.Nm
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utility is compliant with the
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.St -p1003.1-2008
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specification.
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.Pp
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The flags
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.Op Fl adjrtz ,
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as well as the conversion specifiers
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.Ql \&%F ,
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.Ql \&%G ,
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.Ql \&%g ,
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.Ql \&%k ,
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.Ql \&%l ,
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.Ql \&%R ,
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.Ql \&%s ,
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.Ql \&%v ,
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and
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.Ql \&%+ ,
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are extensions to that specification.
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.Pp
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This implementation requires the traditional
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.Bx
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date format,
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[[[[[cc]yy]mm]dd]HH]MM[.SS],
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which differs from the
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X/Open System Interfaces option of the
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.St -p1003.1-2008
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specification.
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.Sh HISTORY
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A
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.Nm
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command appeared in
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.At v1 .
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