DATE(1) | General Commands Manual | DATE(1) |
date
— display or
set date and time
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] |
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-I
[FMT]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
-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
-R
%a, %d %b %Y %T %z
” as
output_fmt while LC_TIME
is
set to the “C” locale .-r
seconds-r
filename-u
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
]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:
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.
The following environment variable affects the execution of
date
:
TZ
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.
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.
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.
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).
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.
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.
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.
July 28, 2022 | macOS 14.6 |