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984263bc
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1.\" Copyright (c) 1980, 1990, 1993
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" This code is derived from software contributed to Berkeley by
5.\" the Institute of Electrical and Electronics Engineers, Inc.
6.\"
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8.\" modification, are permitted provided that the following conditions
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10.\" 1. Redistributions of source code must retain the above copyright
11.\" notice, this list of conditions and the following disclaimer.
12.\" 2. Redistributions in binary form must reproduce the above copyright
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15.\" 3. All advertising materials mentioning features or use of this software
16.\" must display the following acknowledgement:
17.\" This product includes software developed by the University of
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19.\" 4. Neither the name of the University nor the names of its contributors
20.\" may be used to endorse or promote products derived from this software
21.\" without specific prior written permission.
22.\"
23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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34.\"
35.\" @(#)date.1 8.3 (Berkeley) 4/28/95
36.\" $FreeBSD: src/bin/date/date.1,v 1.34.2.15 2003/02/24 03:01:00 trhodes Exp $
1de703da 37.\" $DragonFly: src/bin/date/date.1,v 1.2 2003/06/17 04:22:49 dillon Exp $
984263bc
MD
38.\"
39.Dd November 17, 1993
40.Dt DATE 1
41.Os
42.Sh NAME
43.Nm date
44.Nd display or set date and time
45.Sh SYNOPSIS
46.Nm
47.Op Fl jnu
48.Op Fl d Ar dst
49.Op Fl r Ar seconds
50.Op Fl t Ar minutes_west
51.Oo
52.Fl v
53.Sm off
54.Op Cm + | -
55.Ar val Op Ar ymwdHMS
56.Sm on
57.Oc
58.Ar ...
59.Oo
60.Fl f
61.Ar fmt date |
62.Sm off
63.Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
64.Ar MM Op Ar .ss
65.Sm on
66.Oc
67.Op Cm + Ns Ar format
68.Sh DESCRIPTION
69When invoked without arguments, the
70.Nm
71utility displays the current date and time.
72Otherwise, depending on the options specified,
73.Nm
74will set the date and time or print it in a user-defined way.
75.Pp
76The
77.Nm
78utility displays the date and time read from the kernel clock.
79When used to set the date and time,
80both the kernel clock and the hardware clock are updated.
81.Pp
82Only the superuser may set the date,
83and if the system securelevel (see
84.Xr securelevel 8 )
85is greater than 1,
86the time may not be changed by more than 1 second.
87.Pp
88The options are as follows:
89.Bl -tag -width Ds
90.It Fl d Ar dst
91Set the kernel's value for daylight saving time.
92If
93.Ar dst
94is non-zero, future calls
95to
96.Xr gettimeofday 2
97will return a non-zero for
98.Fa tz_dsttime .
99.It Fl f
100Use
101.Ar fmt
102as the format string to parse the
103.Ar date
104provided rather than using the default
105.Sm off
106.Oo Oo Oo Oo Oo
107.Ar cc Oc
108.Ar yy Oc
109.Ar mm Oc
110.Ar dd Oc
111.Ar HH
112.Oc Ar MM Op Ar .ss
113.Sm on
114format.
115Parsing is done using
116.Xr strptime 3 .
117.It Fl j
118Do not try to set the date.
119This allows you to use the
120.Fl f
121flag in addition to the
122.Cm +
123option to convert one date format to another.
124.It Fl n
125By default, if the
126.Xr timed 8
127daemon is running,
128.Nm
129sets the time on all of the machines in the local group.
130The
131.Fl n
132option suppresses this behavior and causes the time to be set only on the
133current machine.
134.It Fl r Ar seconds
135Print the date and time represented by
136.Ar seconds ,
137where
138.Ar seconds
139is the number of seconds since the Epoch
140(00:00:00 UTC, January 1, 1970;
141see
142.Xr time 3 ) ,
143and can be specified in decimal, octal, or hex.
144.It Fl t Ar minutes_west
145Set the system's value for minutes west of
146.Tn GMT .
147.Ar minutes_west
148specifies the number of minutes returned in
149.Fa tz_minuteswest
150by future calls to
151.Xr gettimeofday 2 .
152.It Fl u
153Display or set the date in
154.Tn UTC
155(Coordinated Universal) time.
156.It Fl v
157Adjust (i.e., take the current date and display the result of the
158adjustment; not actually set the date) the second, minute, hour, month
159day, week day, month or year according to
160.Ar val .
161If
162.Ar val
163is preceded with a plus or minus sign,
164the date is adjusted forwards or backwards according to the remaining string,
165otherwise the relevant part of the date is set.
166The date can be adjusted as many times as required using these flags.
167Flags are processed in the order given.
168.Pp
169When setting values
170(rather than adjusting them),
171seconds are in the range 0-59, minutes are in the range 0-59, hours are
172in the range 0-23, month days are in the range 1-31, week days are in the
173range 0-6 (Sun-Sat),
174months are in the range 1-12 (Jan-Dec)
175and years are in the range 80-38 or 1980-2038.
176.Pp
177If
178.Ar val
179is numeric, one of either
180.Ar y ,
181.Ar m ,
182.Ar w ,
183.Ar d ,
184.Ar H ,
185.Ar M
186or
187.Ar S
188must be used to specify which part of the date is to be adjusted.
189.Pp
190The week day or month may be specified using a name rather than a
191number.
192If a name is used with the plus
193(or minus)
194sign, the date will be put forwards
195(or backwards)
196to the next
197(previous)
198date that matches the given week day or month.
199This will not adjust the date,
200if the given week day or month is the same as the current one.
201.Pp
202When a date is adjusted to a specific value or in units greater than hours,
203daylight savings time considerations are ignored.
204Adjustments in units of hours or less honor daylight saving time.
205So, assuming the current date is March 26, 0:30 and that the DST adjustment
206means that the clock goes forward at 01:00 to 02:00, using
207.Fl v No +1H
208will adjust the date to March 26, 2:30.
209Likewise, if the date is October 29, 0:30 and the DST adjustment means that
210the clock goes back at 02:00 to 01:00, using
211.Fl v No +3H
212will be necessary to reach October 29, 2:30.
213.Pp
214When the date is adjusted to a specific value that doesn't actually exist
215(for example March 26, 1:30 BST 2000 in the Europe/London timezone),
216the date will be silently adjusted forwards in units of one hour until it
217reaches a valid time.
218When the date is adjusted to a specific value that occurs twice
219(for example October 29, 1:30 2000),
220the resulting timezone will be set so that the date matches the earlier of
221the two times.
222.Pp
223Refer to the examples below for further details.
224.El
225.Pp
226An operand with a leading plus
227.Pq Sq +
228sign signals a user-defined format string
229which specifies the format in which to display the date and time.
230The format string may contain any of the conversion specifications
231described in the
232.Xr strftime 3
233manual page, as well as any arbitrary text.
234A newline
235.Pq Ql \en
236character is always output after the characters specified by
237the format string.
238The format string for the default display is
239.Dq +%+ .
240.Pp
241If an operand does not have a leading plus sign, it is interpreted as
242a value for setting the system's notion of the current date and time.
243The canonical representation for setting the date and time is:
244.Pp
245.Bl -tag -width Ds -compact -offset indent
246.It Ar cc
247Century
248(either 19 or 20)
249prepended to the abbreviated year.
250.It Ar yy
251Year in abbreviated form
252(e.g. 89 for 1989, 06 for 2006).
253.It Ar mm
254Numeric month, a number from 1 to 12.
255.It Ar dd
256Day, a number from 1 to 31.
257.It Ar HH
258Hour, a number from 0 to 23.
259.It Ar MM
260Minutes, a number from 0 to 59.
261.It Ar ss
262Seconds, a number from 0 to 61
263(59 plus a maximum of two leap seconds).
264.El
265.Pp
266Everything but the minutes is optional.
267.Pp
268Time changes for Daylight Saving Time, standard time, leap seconds,
269and leap years are handled automatically.
270.Sh EXAMPLES
271The command:
272.Pp
273.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
274.Pp
275will display:
276.Bd -literal -offset indent
277DATE: 1987-11-21
278TIME: 13:36:16
279.Ed
280.Pp
281In the Europe/London timezone, the command:
282.Pp
283.Dl "date -v1m -v+1y"
284.Pp
285will display:
286.Pp
287.Dl "Sun Jan 4 04:15:24 GMT 1998"
288.Pp
289where it is currently Mon Aug 4 04:15:24 BST 1997.
290.Pp
291The command:
292.Pp
293.Dl "date -v1d -v3m -v0y -v-1d"
294.Pp
295will display the last day of February in the year 2000:
296.Pp
297.Dl "Tue Feb 29 03:18:00 GMT 2000"
298.Pp
299The command:
300.Pp
301.Dl "date -v1d -v+1m -v-1d -v-fri"
302.Pp
303will display the last Friday of the month:
304.Pp
305.Dl "Fri Aug 29 04:31:11 BST 1997"
306.Pp
307where it is currently Mon Aug 4 04:31:11 BST 1997.
308.Pp
309The command:
310.Pp
311.Dl "date 8506131627"
312.Pp
313sets the date to
314.Dq Li "June 13, 1985, 4:27 PM" .
315.Pp
316.Dl "date ""+%Y%m%d%H%M.%S"""
317.Pp
318may be used on one machine to print out the date
319suitable for setting on another.
320.Pp
321The command:
322.Pp
323.Dl "date 1432"
324.Pp
325sets the time to
326.Li "2:32 PM" ,
327without modifying the date.
328.Sh ENVIRONMENT
329The following environment variables affect the execution of
330.Nm :
331.Bl -tag -width Ds
332.It Ev TZ
333The timezone to use when displaying dates.
334The normal format is a pathname relative to
335.Pa /usr/share/zoneinfo .
336For example, the command
337.Dq TZ=America/Los_Angeles date
338displays the current time in California.
339See
340.Xr environ 7
341for more information.
342.El
343.Sh FILES
344.Bl -tag -width /var/log/messages -compact
345.It Pa /var/log/wtmp
346record of date resets and time changes
347.It Pa /var/log/messages
348record of the user setting the time
349.El
350.Sh SEE ALSO
351.Xr gettimeofday 2 ,
352.Xr strftime 3 ,
353.Xr strptime 3 ,
354.Xr utmp 5 ,
355.Xr timed 8
356.Rs
357.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
358.%A R. Gusella
359.%A S. Zatti
360.Re
361.Sh DIAGNOSTICS
362The
363.Nm
364utility exits 0 on success, 1 if unable to set the date, and 2
365if able to set the local date, but unable to set it globally.
366.Pp
367Occasionally, when
368.Xr timed 8
369synchronizes the time on many hosts, the setting of a new time value may
370require more than a few seconds.
371On these occasions,
372.Nm
373prints:
374.Ql Network time being set .
375The message
376.Ql Communication error with timed
377occurs when the communication
378between
379.Nm
380and
381.Xr timed 8
382fails.
383.Sh STANDARDS
384The
385.Nm
386utility is expected to be compatible with
387.St -p1003.2 .
388.Sh HISTORY
389A
390.Nm
391command appeared in
392.At v1 .