xref: /freebsd/bin/date/date.1 (revision c98323078dede7579020518ec84cdcb478e5c142)
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.\"
7.\" Redistribution and use in source and binary forms, with or without
8.\" modification, are permitted provided that the following conditions
9.\" are met:
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
13.\"    notice, this list of conditions and the following disclaimer in the
14.\"    documentation and/or other materials provided with the distribution.
15.\" 4. Neither the name of the University nor the names of its contributors
16.\"    may be used to endorse or promote products derived from this software
17.\"    without specific prior written permission.
18.\"
19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29.\" SUCH DAMAGE.
30.\"
31.\"     @(#)date.1	8.3 (Berkeley) 4/28/95
32.\" $FreeBSD$
33.\"
34.Dd November 17, 1993
35.Dt DATE 1
36.Os
37.Sh NAME
38.Nm date
39.Nd display or set date and time
40.Sh SYNOPSIS
41.Nm
42.Op Fl ju
43.Op Fl r Ar seconds
44.Oo
45.Fl v
46.Sm off
47.Op Cm + | -
48.Ar val Op Ar ymwdHMS
49.Sm on
50.Oc
51.Ar ...
52.Op Cm + Ns Ar output_fmt
53.Nm
54.Op Fl jnu
55.Sm off
56.Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
57.Ar MM Op Ar .ss
58.Sm on
59.Nm
60.Op Fl jnu
61.Fl f Ar input_fmt new_date
62.Op Cm + Ns Ar output_fmt
63.Nm
64.Op Fl d Ar dst
65.Op Fl t Ar minutes_west
66.Sh DESCRIPTION
67When invoked without arguments, the
68.Nm
69utility displays the current date and time.
70Otherwise, depending on the options specified,
71.Nm
72will set the date and time or print it in a user-defined way.
73.Pp
74The
75.Nm
76utility displays the date and time read from the kernel clock.
77When used to set the date and time,
78both the kernel clock and the hardware clock are updated.
79.Pp
80Only the superuser may set the date,
81and if the system securelevel (see
82.Xr securelevel 8 )
83is greater than 1,
84the time may not be changed by more than 1 second.
85.Pp
86The options are as follows:
87.Bl -tag -width Ds
88.It Fl d Ar dst
89Set the kernel's value for daylight saving time.
90If
91.Ar dst
92is non-zero, future calls
93to
94.Xr gettimeofday 2
95will return a non-zero for
96.Fa tz_dsttime .
97.It Fl f
98Use
99.Ar input_fmt
100as the format string to parse the
101.Ar new_date
102provided rather than using the default
103.Sm off
104.Oo Oo Oo Oo Oo
105.Ar cc Oc
106.Ar yy Oc
107.Ar mm Oc
108.Ar dd Oc
109.Ar HH
110.Oc Ar MM Op Ar .ss
111.Sm on
112format.
113Parsing is done using
114.Xr strptime 3 .
115.It Fl j
116Do not try to set the date.
117This allows you to use the
118.Fl f
119flag in addition to the
120.Cm +
121option to convert one date format to another.
122.It Fl n
123By default, if the
124.Xr timed 8
125daemon is running,
126.Nm
127sets the time on all of the machines in the local group.
128The
129.Fl n
130option suppresses this behavior and causes the time to be set only on the
131current machine.
132.It Fl r Ar seconds
133Print the date and time represented by
134.Ar seconds ,
135where
136.Ar seconds
137is the number of seconds since the Epoch
138(00:00:00 UTC, January 1, 1970;
139see
140.Xr time 3 ) ,
141and can be specified in decimal, octal, or hex.
142.It Fl t Ar minutes_west
143Set the system's value for minutes west of
144.Tn GMT .
145.Ar minutes_west
146specifies the number of minutes returned in
147.Fa tz_minuteswest
148by future calls to
149.Xr gettimeofday 2 .
150.It Fl u
151Display or set the date in
152.Tn UTC
153(Coordinated Universal) time.
154.It Fl v
155Adjust (i.e., take the current date and display the result of the
156adjustment; not actually set the date) the second, minute, hour, month
157day, week day, month or year according to
158.Ar val .
159If
160.Ar val
161is preceded with a plus or minus sign,
162the date is adjusted forwards or backwards according to the remaining string,
163otherwise the relevant part of the date is set.
164The date can be adjusted as many times as required using these flags.
165Flags are processed in the order given.
166.Pp
167When setting values
168(rather than adjusting them),
169seconds are in the range 0-59, minutes are in the range 0-59, hours are
170in the range 0-23, month days are in the range 1-31, week days are in the
171range 0-6 (Sun-Sat),
172months are in the range 1-12 (Jan-Dec)
173and years are in the range 80-38 or 1980-2038.
174.Pp
175If
176.Ar val
177is numeric, one of either
178.Ar y ,
179.Ar m ,
180.Ar w ,
181.Ar d ,
182.Ar H ,
183.Ar M
184or
185.Ar S
186must be used to specify which part of the date is to be adjusted.
187.Pp
188The week day or month may be specified using a name rather than a
189number.
190If a name is used with the plus
191(or minus)
192sign, the date will be put forwards
193(or backwards)
194to the next
195(previous)
196date that matches the given week day or month.
197This will not adjust the date,
198if the given week day or month is the same as the current one.
199.Pp
200When a date is adjusted to a specific value or in units greater than hours,
201daylight savings time considerations are ignored.
202Adjustments in units of hours or less honor daylight saving time.
203So, assuming the current date is March 26, 0:30 and that the DST adjustment
204means that the clock goes forward at 01:00 to 02:00, using
205.Fl v No +1H
206will adjust the date to March 26, 2:30.
207Likewise, if the date is October 29, 0:30 and the DST adjustment means that
208the clock goes back at 02:00 to 01:00, using
209.Fl v No +3H
210will be necessary to reach October 29, 2:30.
211.Pp
212When the date is adjusted to a specific value that doesn't actually exist
213(for example March 26, 1:30 BST 2000 in the Europe/London timezone),
214the date will be silently adjusted forwards in units of one hour until it
215reaches a valid time.
216When the date is adjusted to a specific value that occurs twice
217(for example October 29, 1:30 2000),
218the resulting timezone will be set so that the date matches the earlier of
219the two times.
220.Pp
221Refer to the examples below for further details.
222.El
223.Pp
224An operand with a leading plus
225.Pq Sq +
226sign signals a user-defined format string
227which specifies the format in which to display the date and time.
228The format string may contain any of the conversion specifications
229described in the
230.Xr strftime 3
231manual page, as well as any arbitrary text.
232A newline
233.Pq Ql \en
234character is always output after the characters specified by
235the format string.
236The format string for the default display is
237.Dq +%+ .
238.Pp
239If an operand does not have a leading plus sign, it is interpreted as
240a value for setting the system's notion of the current date and time.
241The canonical representation for setting the date and time is:
242.Pp
243.Bl -tag -width Ds -compact -offset indent
244.It Ar cc
245Century
246(either 19 or 20)
247prepended to the abbreviated year.
248.It Ar yy
249Year in abbreviated form
250(e.g., 89 for 1989, 06 for 2006).
251.It Ar mm
252Numeric month, a number from 1 to 12.
253.It Ar dd
254Day, a number from 1 to 31.
255.It Ar HH
256Hour, a number from 0 to 23.
257.It Ar MM
258Minutes, a number from 0 to 59.
259.It Ar ss
260Seconds, a number from 0 to 61
261(59 plus a maximum of two leap seconds).
262.El
263.Pp
264Everything but the minutes is optional.
265.Pp
266Time changes for Daylight Saving Time, standard time, leap seconds,
267and leap years are handled automatically.
268.Sh EXAMPLES
269The command:
270.Pp
271.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
272.Pp
273will display:
274.Bd -literal -offset indent
275DATE: 1987-11-21
276TIME: 13:36:16
277.Ed
278.Pp
279In the Europe/London timezone, the command:
280.Pp
281.Dl "date -v1m -v+1y"
282.Pp
283will display:
284.Pp
285.Dl "Sun Jan  4 04:15:24 GMT 1998"
286.Pp
287where it is currently
288.Li "Mon Aug  4 04:15:24 BST 1997" .
289.Pp
290The command:
291.Pp
292.Dl "date -v1d -v3m -v0y -v-1d"
293.Pp
294will display the last day of February in the year 2000:
295.Pp
296.Dl "Tue Feb 29 03:18:00 GMT 2000"
297.Pp
298The command:
299.Pp
300.Dl "date -v1d -v+1m -v-1d -v-fri"
301.Pp
302will display the last Friday of the month:
303.Pp
304.Dl "Fri Aug 29 04:31:11 BST 1997"
305.Pp
306where it is currently
307.Li "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.Qq ( Li "+%m%d%H%M%Y.%S"
321for use on
322.Tn Linux . )
323.Pp
324The command:
325.Pp
326.Dl "date 1432"
327.Pp
328sets the time to
329.Li "2:32 PM" ,
330without modifying the date.
331.Pp
332Finally the command:
333.Pp
334.Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
335.Pp
336can be used to parse the ouput from
337.Nm
338and express it in epoch time.
339.Sh ENVIRONMENT
340The following environment variables affect the execution of
341.Nm :
342.Bl -tag -width Ds
343.It Ev TZ
344The timezone to use when displaying dates.
345The normal format is a pathname relative to
346.Pa /usr/share/zoneinfo .
347For example, the command
348.Dq TZ=America/Los_Angeles date
349displays the current time in California.
350See
351.Xr environ 7
352for more information.
353.El
354.Sh FILES
355.Bl -tag -width /var/log/messages -compact
356.It Pa /var/log/wtmp
357record of date resets and time changes
358.It Pa /var/log/messages
359record of the user setting the time
360.El
361.Sh SEE ALSO
362.Xr gettimeofday 2 ,
363.Xr strftime 3 ,
364.Xr strptime 3 ,
365.Xr utmp 5 ,
366.Xr timed 8
367.Rs
368.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
369.%A R. Gusella
370.%A S. Zatti
371.Re
372.Sh DIAGNOSTICS
373The
374.Nm
375utility exits 0 on success, 1 if unable to set the date, and 2
376if able to set the local date, but unable to set it globally.
377.Pp
378Occasionally, when
379.Xr timed 8
380synchronizes the time on many hosts, the setting of a new time value may
381require more than a few seconds.
382On these occasions,
383.Nm
384prints:
385.Ql Network time being set .
386The message
387.Ql Communication error with timed
388occurs when the communication
389between
390.Nm
391and
392.Xr timed 8
393fails.
394.Sh STANDARDS
395The
396.Nm
397utility is expected to be compatible with
398.St -p1003.2 .
399.Sh HISTORY
400A
401.Nm
402command appeared in
403.At v1 .
404