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Editing: date.1
.\"- .\" 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. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)date.1 8.3 (Berkeley) 4/28/95 .\" $FreeBSD$ .\" .Dd August 25, 2020 .Dt DATE 1 .Os .Sh NAME .Nm date .Nd display or set date and time .Sh SYNOPSIS .Nm .Op Fl jnRu .Op Fl r Ar seconds | Ar filename .Oo .Fl v .Sm off .Op Cm + | - .Ar val Op Ar ymwdHMS .Sm on .Oc .Ar ... .Op Cm + Ns Ar output_fmt .Nm .Op Fl ju .Sm off .Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH .Ar MM Op Ar .ss .Sm on .Nm .Op Fl jRu .Fl f Ar input_fmt new_date .Op Cm + Ns Ar output_fmt .Nm .Op Fl jnu .Op Fl I Ns Op Ar FMT .Op Fl f Ar input_fmt .Op Fl r Ar ... .Op Fl v Ar ... .Op Ar new_date .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 The .Nm utility displays the date and time read from the kernel clock. When used to set the date and time, both the kernel clock and the hardware clock are updated. .Pp Only the superuser may set the date, and if the system securelevel (see .Xr securelevel 7 ) is greater than 1, the time may not be changed by more than 1 second. .Pp The options are as follows: .Bl -tag -width Ds .It Fl f Use .Ar input_fmt as the format string to parse the .Ar new_date provided rather than using the default .Sm off .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 .Sm on format. Parsing is done using .Xr strptime 3 . .It Fl I Ns Op Ar FMT Use .St -iso8601 output format. .Ar FMT may be omitted, in which case the default is .Sq date . Valid .Ar FMT values are .Sq date , .Sq hours , .Sq minutes , and .Sq seconds . The date and time is formatted to the specified precision. When .Ar FMT is .Sq hours (or the more precise .Sq minutes or .Sq seconds ) , the .St -iso8601 format includes the timezone. .It Fl j Do not try to set the date. This allows you to use the .Fl f flag in addition to the .Cm + option to convert one date format to another. Note that any date or time components unspecified by the .Fl f format string take their values from the current time. .It Fl n Obsolete flag, accepted and ignored for compatibility. .It Fl R Use RFC 2822 date and time output format. This is equivalent to using .Dq Li %a, %d %b %Y \&%T %z as .Ar output_fmt while .Ev LC_TIME is set to the .Dq C locale . .It Fl r Ar seconds Print the date and time represented by .Ar seconds , where .Ar seconds is the number of seconds since the Epoch (00:00:00 UTC, January 1, 1970; see .Xr time 3 ) , and can be specified in decimal, octal, or hex. .It Fl r Ar filename Print the date and time of the last modification of .Ar filename . .It Fl u Display or set the date in .Tn UTC (Coordinated Universal) time. .It Fl v Adjust (i.e., take the current date and display the result of the adjustment; not actually set the date) the second, minute, hour, month day, week day, month or year according to .Ar val . If .Ar val is preceded with a plus or minus sign, the date is adjusted forwards or backwards according to the remaining string, otherwise the relevant part of the date is set. The date can be adjusted as many times as required using these flags. Flags are processed in the order given. .Pp When setting values (rather than adjusting them), seconds are in the range 0-59, minutes are in the range 0-59, hours are in the range 0-23, month days are in the range 1-31, week days are in the range 0-6 (Sun-Sat), months are in the range 1-12 (Jan-Dec) and years are in the range 80-38 or 1980-2038. .Pp If .Ar val is numeric, one of either .Ar y , .Ar m , .Ar w , .Ar d , .Ar H , .Ar M or .Ar S must be used to specify which part of the date is to be adjusted. .Pp The week day or month may be specified using a name rather than a number. If a name is used with the plus (or minus) sign, the date will be put forwards (or backwards) to the next (previous) date that matches the given week day or month. This will not adjust the date, if the given week day or month is the same as the current one. .Pp When a date is adjusted to a specific value or in units greater than hours, daylight savings time considerations are ignored. Adjustments in units of hours or less honor daylight saving time. So, assuming the current date is March 26, 0:30 and that the DST adjustment means that the clock goes forward at 01:00 to 02:00, using .Fl v No +1H will adjust the date to March 26, 2:30. Likewise, if the date is October 29, 0:30 and the DST adjustment means that the clock goes back at 02:00 to 01:00, using .Fl v No +3H will be necessary to reach October 29, 2:30. .Pp When the date is adjusted to a specific value that does not actually exist (for example March 26, 1:30 BST 2000 in the Europe/London timezone), the date will be silently adjusted forwards in units of one hour until it reaches a valid time. When the date is adjusted to a specific value that occurs twice (for example October 29, 1:30 2000), the resulting timezone will be set so that the date matches the earlier of the two times. .Pp It is not possible to adjust a date to an invalid absolute day, so using the switches .Fl v No 31d Fl v No 12m will simply fail five months of the year. It is therefore usual to set the month before setting the day; using .Fl v No 12m Fl v No 31d always works. .Pp Adjusting the date by months is inherently ambiguous because a month is a unit of variable length depending on the current date. This kind of date adjustment is applied in the most intuitive way. First of all, .Nm tries to preserve the day of the month. If it is impossible because the target month is shorter than the present one, the last day of the target month will be the result. For example, using .Fl v No +1m on May 31 will adjust the date to June 30, while using the same option on January 30 will result in the date adjusted to the last day of February. This approach is also believed to make the most sense for shell scripting. Nevertheless, be aware that going forth and back by the same number of months may take you to a different date. .Pp Refer to the examples below for further details. .El .Pp An operand with a leading plus .Pq Sq + sign 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 .Dq +%+ . .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 cc Century (either 19 or 20) prepended to the abbreviated year. .It Ar yy Year in abbreviated form (e.g., 89 for 1989, 06 for 2006). .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 Minutes, a number from 0 to 59. .It Ar ss Seconds, a number from 0 to 60 (59 plus a potential leap second). .El .Pp Everything but the minutes is optional. .Pp Time changes for Daylight Saving Time, standard time, leap seconds, and leap years are handled automatically. .Sh ENVIRONMENT The following environment variables affect the execution of .Nm : .Bl -tag -width Ds .It Ev TZ The timezone to use when displaying dates. The normal format is a pathname relative to .Pa /usr/share/zoneinfo . For example, the command .Dq TZ=America/Los_Angeles date displays the current time in California. See .Xr environ 7 for more information. .El .Sh FILES .Bl -tag -width /var/log/messages -compact .It Pa /var/log/utx.log 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 The command: .Pp .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S""" .Pp will display: .Bd -literal -offset indent DATE: 1987-11-21 TIME: 13:36:16 .Ed .Pp In the Europe/London timezone, the command: .Pp .Dl "date -v1m -v+1y" .Pp will display: .Pp .Dl "Sun Jan 4 04:15:24 GMT 1998" .Pp where it is currently .Li "Mon Aug 4 04:15:24 BST 1997" . .Pp The command: .Pp .Dl "date -v1d -v3m -v0y -v-1d" .Pp will display the last day of February in the year 2000: .Pp .Dl "Tue Feb 29 03:18:00 GMT 2000" .Pp So will the command: .Pp .Dl "date -v3m -v30d -v0y -v-1m" .Pp because there is no such date as the 30th of February. .Pp The command: .Pp .Dl "date -v1d -v+1m -v-1d -v-fri" .Pp will display the last Friday of the month: .Pp .Dl "Fri Aug 29 04:31:11 BST 1997" .Pp where it is currently .Li "Mon Aug 4 04:31:11 BST 1997" . .Pp The command: .Pp .Dl "date 8506131627" .Pp sets the date to .Dq Li "June 13, 1985, 4:27 PM" . .Pp .Dl "date ""+%Y%m%d%H%M.%S""" .Pp may be used on one machine to print out the date suitable for setting on another. .Qq ( Li "+%m%d%H%M%Y.%S" for use on .Tn Linux . ) .Pp The command: .Pp .Dl "date 1432" .Pp sets the time to .Li "2:32 PM" , without modifying the date. .Pp The command .Pp .Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339" .Pp will display .Pp .Dl "2018-08-04T13:42:19-07:00" .Pp Finally the command: .Pp .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s""" .Pp can be used to parse the output from .Nm and express it in Epoch time. .Sh DIAGNOSTICS It is invalid to combine the .Fl I flag with either .Fl R or an output format .Dq ( + Ns ... ) operand. If this occurs, .Nm prints: .Ql multiple output formats specified and exits with an error status. .Sh SEE ALSO .Xr locale 1 , .Xr gettimeofday 2 , .Xr getutxent 3 , .Xr strftime 3 , .Xr strptime 3 .Rs .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" .%A R. Gusella .%A S. Zatti .Re .Sh STANDARDS The .Nm utility is expected to be compatible with .St -p1003.2 . The .Fl d , f , I , j , r , t , and .Fl v options are all extensions to the standard. .Pp The format selected by the .Fl I flag is compatible with .St -iso8601 . .Sh HISTORY A .Nm command appeared in .At v1 . .Pp The .Fl I flag was added in .Fx 12.0 .
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