.\"	$OpenBSD: date.1,v 1.56 2011/03/11 21:36:09 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.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    may be used to endorse or promote products derived from this software
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.\"     @(#)date.1	8.3 (Berkeley) 4/28/95
.\"
.Dd $Mdocdate: March 11 2011 $
.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 Fl z Ar output_zone
.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
Changing the system date has some risks, as described in
.Xr settimeofday 2 .
Only the superuser may change 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.
.It Fl z Ar output_zone
Just before printing the time, change to the specified timezone;
see the description of
.Ev TZ
below.
This can be used with
.Fl j
to easily convert time specifications from one zone to another.
.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 parsing or 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 EXIT STATUS
The
.Nm
utility exits 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.
.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 198506131627
.Pp
Set the time to
2:32 PM,
without modifying the date:
.Pp
.Dl # date 1432
.Sh DIAGNOSTICS
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 compliant with the
.St -p1003.1-2008
specification.
.Pp
The flags
.Op Fl adjnrtz
are extensions to that specification.
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .