-.\" $NetBSD: date.1,v 1.22 1998/06/08 09:07:13 lukem Exp $
-.\"
+.\"-
.\" Copyright (c) 1980, 1990, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" 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. All advertising materials mentioning features or use of this software
-.\" must display the following acknowledgement:
-.\" This product includes software developed by the University of
-.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
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.\" SUCH DAMAGE.
.\"
.\" @(#)date.1 8.3 (Berkeley) 4/28/95
+.\" $FreeBSD$
.\"
-.Dd January 20, 1998
+.Dd May 7, 2015
.Dt DATE 1
.Os
.Sh NAME
.Nd display or set date and time
.Sh SYNOPSIS
.Nm
-.Op Fl nu
-.Op Fl r Ar seconds
-.Op Cm + Ns Ar format
-.Nm ""
-.Ar [[[[[cc]yy]mm]dd]hh]mm[\&.ss]
+.Op Fl jRu
+.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 jnu
+.Sm off
+.Op Oo Oo Ar mm Oc Ar dd Oc Ar HH
+.Ar MM Oo Oo Ar cc Oc Ar yy Oc Op Ar .ss
+.Sm on
+.Nm
+.Op Fl jnRu
+.Fl f Ar input_fmt new_date
+.Op Cm + Ns Ar output_fmt
+.Nm
+.Op Fl d Ar dst
+.Op Fl t Ar minutes_west
.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
-displays the current date and time when invoked without arguments.
-Providing arguments will format the date and time in a user-defined
-way or set the date.
-Only the superuser may set the date.
+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 d Ar dst
+Set the kernel's value for daylight saving time.
+If
+.Ar dst
+is non-zero, future calls
+to
+.Xr gettimeofday 2
+will return a non-zero for
+.Fa tz_dsttime .
+.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
+.Ar mm Oc
+.Ar dd Oc
+.Ar HH Oc
+.Ar MM
+.Oo Oo
+.Ar cc Oc
+.Ar yy Oc Oo
+.Ar .ss Oc
+.Sm on
+format.
+Parsing is done using
+.Xr strptime 3 .
+.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.
.It Fl n
-The utility
+By default, if the
.Xr timed 8
-is used to synchronize the clocks on groups of machines.
-By default, if
-timed
-is running,
+daemon is running,
.Nm
-will set the time on all of the machines in the local group.
+sets the time on all of the machines in the local group.
The
.Fl n
-option stops
-.Nm
-from setting the time for other than the current machine.
-.It Fl r
-Print out the date and time that is
+option suppresses this behavior and causes the time to be set only on the
+current machine.
+.It Fl R
+Use RFC 2822 date and time output format. This is equivalent to use
+.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
-from the Epoch.
+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 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
.Tn UTC
-(universal) time.
+(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 (``+'') 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
+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> character is always output after the characters specified by
+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
+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.
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ar cc
-The first two digits of the year (the century).
+Century
+(either 19 or 20)
+prepended to the abbreviated year.
.It Ar yy
-The second two digits of the year. If
-.Dq yy
-is specified, but
-.Dq cc
-is not, a value for
-.Dq yy
-between 69 and 99 results in a
-.Dq cc
-value of 19. Otherwise, a
-.Dq cc
-value of 20 is used.
+Year in abbreviated form
+(e.g., 89 for 1989, 06 for 2006).
.It Ar mm
-The month of the year, from 1 to 12.
+Numeric month, a number from 1 to 12.
.It Ar dd
-The day of the month, from 1 to 31.
-.It Ar hh
-The hour of the day, from 0 to 23.
-.It Ar mm
-The minute of the hour, from 0 to 59.
+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
-The second of the minute, from 0 to 61.
+Seconds, a number from 0 to 61
+(59 plus a maximum of two leap seconds).
.El
.Pp
Everything but the minutes is optional.
.Pp
-Time changes for Daylight Saving and Standard time and leap seconds
-and years are handled automatically.
+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/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:
-.Bd -literal -offset indent
-date "+DATE: %m/%d/%y%nTIME: %H:%M:%S"
-.Ed
+.Pp
+.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
.Pp
will display:
.Bd -literal -offset indent
-DATE: 11/21/87
+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:
-.Bd -literal -offset indent
-date 8506131627
-.Ed
+.Pp
+.Dl "date 0613162785"
.Pp
sets the date to
.Dq Li "June 13, 1985, 4:27 PM" .
.Pp
+.Dl "date ""+%m%d%H%M%Y.%S"""
+.Pp
+may be used on one machine to print out the date
+suitable for setting on another.
+.Pp
The command:
-.Bd -literal -offset indent
-date 1432
-.Ed
+.Pp
+.Dl "date 1432"
.Pp
sets the time to
.Li "2:32 PM" ,
without modifying the date.
-.Sh ENVIRONMENT VARIABLES
-The following environment variables affect the execution of
+.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
-:
-.Bl -tag -width TZ
-.It Ev TZ
-The timezone to use when displaying dates.
-See
-.Xr environ 7
-for more information.
-.El
-.Sh FILES
-.Bl -tag -width /var/log/messages -compact
-.It Pa /var/log/wtmp
-A record of date resets and time changes.
-.It Pa /var/log/messages
-A record of the user setting the time.
-.El
-.Sh SEE ALSO
-.Xr gettimeofday 2 ,
-.Xr strftime 3 ,
-.Xr utmp 5 ,
-.Xr timed 8
-.Rs
-.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
-.%A R. Gusella
-.%A S. Zatti
-.Re
+and express it in Epoch time.
.Sh DIAGNOSTICS
-Exit status is 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.
-.Pp
Occasionally, when
.Xr timed 8
synchronizes the time on many hosts, the setting of a new time value may
between
.Nm
and
-timed
+.Xr timed 8
fails.
+.Sh LEGACY SYNOPSIS
+As above, except for the second line, which is:
+.Pp
+.Nm
+.Op Fl jnu
+.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
+.Sh LEGACY DIAGNOSTICS
+When invoked in legacy mode, the following exit values are returned:
+.Bl -tag -width X -compact
+.It 0
+The date was written successfully
+.It 1
+Unable to set the date
+.It 2
+Able to set the local date, but unable to set it globally
+.El
+.Pp
+For more information about legacy mode, see
+.Xr compat 5 .
+.Sh SEE ALSO
+.Xr locale 1 ,
+.Xr gettimeofday 2 ,
+.Xr getutxent 3 ,
+.Xr strftime 3 ,
+.Xr strptime 3 ,
+.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 expected to be compatible with
.St -p1003.2 .
+The
+.Fl d , f , j , n , r , t ,
+and
+.Fl v
+options are all extensions to the standard.
+.Sh HISTORY
+A
+.Nm
+command appeared in
+.At v1 .
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