DATE(1) General Commands Manual DATE(1)
NAME
date – display or set date and time
SYNOPSIS
date [-nRu] [-I[FMT]] [-r filename] [-r seconds]
[-v[+|-]val[y|m|w|d|H|M|S]] [+output_fmt]
date [-jnRu] [-I[FMT]] [-v[+|-]val[y|m|w|d|H|M|S]]
[[[mm]dd]HH]MM[[cc]yy][.SS] [+output_fmt]
date [-jnRu] [-I[FMT]] [-v[+|-]val[y|m|w|d|H|M|S]] -f input_fmt new_date
[+output_fmt]
DESCRIPTION
When invoked without arguments, the date utility displays the current
date and time. Otherwise, depending on the options specified, date will
set the date and time or print it in a user-defined way.
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.
Only the superuser may set the date, and if the system securelevel (see
securelevel(7)) is greater than 1, the time may not be changed by more
than 1 second.
The options are as follows:
-f input_fmt
Use input_fmt as the format string to parse the new_date provided
rather than using the default [[[mm]dd]HH]MM[[cc]yy][.SS] format.
Parsing is done using strptime(3).
-I[FMT]
Use ISO 8601 output format. FMT may be omitted, in which case
the default is date. Valid FMT values are date, hours, minutes,
and seconds. The date and time is formatted to the specified
precision. When FMT is hours (or the more precise minutes or
seconds), the ISO 8601 format includes the timezone.
-j Do not try to set the date. This allows you to use the -f flag
in addition to the + option to convert one date format to
another. Note that any date or time components unspecified by
the -f format string take their values from the current time.
-n Obsolete flag, accepted and ignored for compatibility.
-R Use RFC 2822 date and time output format. This is equivalent to
using “%a, %d %b %Y %T %z” as output_fmt while LC_TIME is set to
the “C” locale .
-r seconds
Print the date and time represented by seconds, where seconds is
the number of seconds since the Epoch (00:00:00 UTC, January 1,
1970; see time(3)), and can be specified in decimal, octal, or
hex.
-r filename
Print the date and time of the last modification of filename.
-u Display or set the date in UTC (Coordinated Universal) time. By
default date displays the time in the time zone described by
/etc/localtime or the TZ environment variable.
-v [+|-]val[y|m|w|d|H|M|S]
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 val. If 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.
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 a limited range depending on the platform.
On i386, years are in the range 69-38 representing 1969-2038. On
every other platform, years 0-68 are accepted and represent
2000-2068, and 69-99 are accepted and represent 1969-1999. In
both cases, years between 100 and 1900 (both included) are
accepted and interpreted as relative to 1900 of the Gregorian
calendar with a limit of 138 on i386 and a much higher limit on
every other platform. Years starting at 1901 are also accepted,
and are interpreted as absolute years.
If val is numeric, one of either y, m, w, d, H, M or S must be
used to specify which part of the date is to be adjusted.
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.
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 -v +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 -v +3H will be
necessary to reach October 29, 2:30.
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.
It is not possible to adjust a date to an invalid absolute day,
so using the switches -v 31d -v 12m will simply fail five months
of the year. It is therefore usual to set the month before
setting the day; using -v 12m -v 31d always works.
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, date 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 -v +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.
Refer to the examples below for further details.
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 strftime(3) manual page, as well as any arbitrary text.
A newline (‘\n’) character is always output after the characters
specified by the format string. The format string for the default
display is “+%+”.
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:
cc Century (either 19 or 20) prepended to the abbreviated
year.
yy Year in abbreviated form (e.g., 89 for 1989, 06 for 2006).
mm Numeric month, a number from 1 to 12.
dd Day, a number from 1 to 31.
HH Hour, a number from 0 to 23.
MM Minutes, a number from 0 to 59.
SS Seconds, a number from 0 to 60 (59 plus a potential leap
second).
Everything but the minutes is optional.
date understands the time zone definitions from the IANA Time Zone
Database, tzdata, located in /usr/share/zoneinfo. Time changes for
Daylight Saving Time, standard time, leap seconds and leap years are
handled automatically.
There are two ways to specify the time zone:
If the file or symlink /etc/localtime exists, it is interpreted as a time
zone definition file, usually in the directory hierarchy
/usr/share/zoneinfo, which contains the time zone definitions from
tzdata.
If the environment variable TZ is set, its value is interpreted as the
name of a time zone definition file, either an absolute path or a
relative path to a time zone definition in /usr/share/zoneinfo. The TZ
variable overrides /etc/localtime.
If the time zone definition file is invalid, date silently reverts to
UTC.
Previous versions of date included the -d (set daylight saving time flag)
and -t (set negative time zone offset) options, but these details are now
handled automatically by tzdata. Modern offsets are positive for time
zones ahead of UTC and negative for time zones behind UTC, but like the
obsolete -t option, the tzdata files in the subdirectory
/usr/share/zoneinfo/Etc still use an older convention where times ahead
of UTC are considered negative.
ENVIRONMENT
The following environment variable affects the execution of date:
TZ The timezone to use when displaying dates. The normal format is
a pathname relative to /usr/share/zoneinfo. For example, the
command “TZ=America/Los_Angeles date” displays the current time
in California. The variable can also specify an absolute path.
See environ(7) for more information.
FILES
/etc/localtime Time zone information file for default system time
zone. May be omitted, in which case the default time
zone is UTC.
/usr/share/zoneinfo
Directory containing time zone information files.
/var/log/messages Record of the user setting the time.
EXIT STATUS
The date 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.
EXAMPLES
The command:
date "+DATE: %Y-%m-%d%nTIME: %H:%M:%S"
will display:
DATE: 1987-11-21
TIME: 13:36:16
In the Europe/London timezone, the command:
date -v1m -v+1y
will display:
Sun Jan 4 04:15:24 GMT 1998
where it is currently Mon Aug 4 04:15:24 BST 1997.
The command:
date -v1d -v3m -v0y -v-1d
will display the last day of February in the year 2000:
Tue Feb 29 03:18:00 GMT 2000
So will the command:
date -v3m -v30d -v0y -v-1m
because there is no such date as the 30th of February.
The command:
date -v1d -v+1m -v-1d -v-fri
will display the last Friday of the month:
Fri Aug 29 04:31:11 BST 1997
where it is currently Mon Aug 4 04:31:11 BST 1997.
The command:
date 0613162785
sets the date to “June 13, 1985, 4:27 PM”.
date "+%m%d%H%M%Y.%S"
may be used on one machine to print out the date suitable for setting on
another.
The command:
date 1432
sets the time to 2:32 PM, without modifying the date.
The command
TZ=America/Los_Angeles date -Iseconds -r 1533415339
will display
2018-08-04T13:42:19-07:00
Finally the command:
date -j -f "%a %b %d %T %Z %Y" "`LC_ALL=C date`" "+%s"
can be used to parse the output from date and express it in Epoch time.
DIAGNOSTICS
It is invalid to combine the -I flag with either -R or an output format
(“+...”) operand. If this occurs, date prints: ‘multiple output formats
specified’ and exits with status 1.
LEGACY SYNOPSIS
As above, except for the second line, which is:
date [-jnu] [[[[[cc]yy]mm]dd]HH]MM[.SS]
For more information about legacy mode, see compat(5).
SEE ALSO
locale(1), gettimeofday(2), getutxent(3), strftime(3), strptime(3),
tzset(3)
R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX
4.3BSD.
Time Zone Database, https://iana.org/time-zones.
STANDARDS
The date utility is expected to be compatible with IEEE Std 1003.2
(“POSIX.2”). With the exception of the -u option, all options are
extensions to the standard.
The format selected by the -I flag is compatible with ISO 8601.
HISTORY
A date command appeared in Version 1 AT&T UNIX.
A number of options were added and then removed again, including the -d
(set DST flag) and -t (set negative time zone offset). Time zones are
now handled by code bundled with tzdata.
The -I flag was added in FreeBSD 12.0.
macOS 15.2 July 28, 2022 macOS 15.2