display or set date and time
When invoked without arguments, the
utility displays the current date and time. Otherwise, depending on the
will set the date
and time or print it in a user-defined way.
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
is greater than 1, the time may not be changed by more than 1 second.
The options are as follows:
- Set the kernel's value for daylight saving time. If
dst is non-zero, future calls to
will return a non-zero for
- Use input_fmt as the format string to
parse the new_date provided rather than
using the default
format. Parsing is done using
- 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.
- 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
- By default, if the
daemon is running,
date sets the time
on all of the machines in the local group. The
-n option suppresses this behavior and
causes the time to be set only on the current machine.
- Use RFC 2822 date and time output format. This is equivalent to using
%a, %d %b %Y %T %z” as
LC_TIME is set to the “C”
- Print the date and time represented by
seconds is the number of seconds since
the Epoch (00:00:00 UTC, January 1, 1970; see
and can be specified in decimal, octal, or hex.
- Print the date and time of the last modification of
- Set the system's value for minutes west of GMT.
minutes_west specifies the number of
minutes returned in tz_minuteswest by
future calls to
- Display or set the date in UTC (Coordinated Universal) time.
- 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 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 the range 80-38 or
If val is numeric, one of either
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
+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
-v 12m will
simply fail five months of the year. It is therefore usual to set the
month before setting the day; using
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
+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
manual page, as well as any arbitrary text. A newline
’) 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:
- Century (either 19 or 20) prepended to the abbreviated year.
- Year in abbreviated form (e.g., 89 for 1989, 06 for 2006).
- Numeric month, a number from 1 to 12.
- Day, a number from 1 to 31.
- Hour, a number from 0 to 23.
- Minutes, a number from 0 to 59.
- Seconds, a number from 0 to 60 (59 plus a potential leap second).
Everything but the minutes is optional.
Time changes for Daylight Saving Time, standard time, leap seconds, and leap
years are handled automatically.
The following environment variables affect the execution of
- 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. See
for more information.
- record of date resets and time changes
- record of the user setting the time
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
date "+DATE: %Y-%m-%d%nTIME:
In the Europe/London timezone, the command:
date -v1m -v+1y
Sun Jan 4 04:15:24 GMT
where it is currently
Mon Aug 4 04:15:24 BST 1997
date -v1d -v3m -v0y
will display the last day of February in the year 2000:
Tue Feb 29 03:18:00 GMT
So will the command:
date -v3m -v30d -v0y
because there is no such date as the 30th of February.
date -v1d -v+1m -v-1d
will display the last Friday of the month:
Fri Aug 29 04:31:11 BST
where it is currently
Mon Aug 4 04:31:11 BST 1997
sets the date to “
June 13, 1985, 4:27 PM
may be used on one machine to print out the date suitable for setting on
” for use on
sets the time to
, without modifying the date.
TZ=America/Los_Angeles date -Iseconds
Finally the command:
date -j -f "%a %b %d %T %Z
%Y" "`date`" "+%s"
can be used to parse the output from
express it in Epoch time.
synchronizes the time on many hosts, the setting of a new time value may
require more than a few seconds. On these occasions,
Network time being set
’. The message
Communication error with timed
when the communication between
It is invalid to combine the
or an output format
(“+...”) operand. If this occurs,
multiple output formats specified
exits with an error status.
R. Gusella and
S. Zatti, TSP: The Time
Synchronization Protocol for UNIX 4.3BSD.
utility is expected to be compatible
with IEEE Std 1003.2
options are all extensions to the
The format selected by the
compatible with ISO 8601
command appeared in
Version 1 AT&T UNIX
flag was added in