date -- display or set date and time
date [-jnu] [-d dst] [-r seconds] [-t minutes_west] [-v
[+|-]val[ymwdHMS]] ... [-f fmt date | [[[[[cc]yy]mm]dd]HH]MM[.ss]]
[+format]
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(8)) is greater than 1, the time may not be changed by more
than 1 second.
The options are as follows:
-d dst Set the kernel's value for daylight saving time. If dst is nonzero,
future calls to gettimeofday(2) will return a non-zero for
tz_dsttime.
-f Use fmt as the format string to parse the date provided rather
than using the default [[[[[cc]yy]mm]dd]HH]MM[.ss] format. Parsing
is done using strptime(3).
-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.
-n By default, if the timed(8) 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.
-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.
-t minutes_west
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 gettimeofday(2).
-u Display or set the date in UTC (Coordinated Universal) time.
-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 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 the range 80-38 or 1980-2038.
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 doesn't 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.
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 61 (59 plus a maximum of two
leap seconds).
Everything but the minutes is optional.
Time changes for Daylight Saving Time, standard time, leap seconds, and
leap years are handled automatically.
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
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 8506131627
sets the date to ``June 13, 1985, 4:27 PM''.
date "+%Y%m%d%H%M.%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 following environment variables affect 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. See environ(7) for more information.
/var/log/wtmp record of date resets and time changes
/var/log/messages record of the user setting the time
gettimeofday(2), strftime(3), strptime(3), utmp(5), timed(8)
R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX
4.3BSD.
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.
Occasionally, when timed(8) synchronizes the time on many hosts, the setting
of a new time value may require more than a few seconds. On these
occasions, date prints: `Network time being set'. The message
`Communication error with timed' occurs when the communication between
date and timed(8) fails.
The date utility is expected to be compatible with IEEE Std 1003.2
(``POSIX.2'').
A date command appeared in Version 1 AT&T UNIX.
FreeBSD 5.2.1 November 17, 1993 FreeBSD 5.2.1 [ Back ] |
