DATE(1) BSD General Commands Manual DATE(1)
NAME
date -- display or set date and time
SYNOPSIS
date [-jnu] [-d dst] [-r seconds] [-t minutes_west] [-v [+|-]val[ymwdHMS]] ... [-f fmt date | [[[[[cc]yy]mm]dd]HH]MM[.ss]] [+format]
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(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 non-zero, 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 sup-
presses 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 ('
') 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.
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
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''.
The command:
date 1432
sets the time to 2:32 PM, without modifying the date.
ENVIRONMENT
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 com-
mand ``TZ=America/Los_Angeles date'' displays the current time in California. See environ(7) for more information.
FILES
/var/log/wtmp record of date resets and time changes
/var/log/messages record of the user setting the time
SEE ALSO
gettimeofday(2), strftime(3), strptime(3), utmp(5), timed(8)
R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX 4.3BSD.
DIAGNOSTICS
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.
STANDARDS
The date utility is expected to be compatible with IEEE Std 1003.2 (``POSIX.2'').
HISTORY
A date command appeared in Version 1 AT&T UNIX.
BSD
November 17, 1993 BSD