NAME
date —
display or set date and
time
SYNOPSIS
date |
[-ajnu]
[-d date]
[-r
seconds]
[+format]
[[[[[[CC]yy]mm]dd]HH]MM[. SS]] |
DESCRIPTION
date displays the current date and time when invoked without
arguments. Providing arguments will format the date and time in a user-defined
way or set the date. Only the superuser may set the date.
The options are as follows:
-
-
- -a
- Use
adjtime(2) to change the
local system time slowly, maintaining it as a monotonically increasing
function. -a implies -n.
-
-
- -d
date
- Parse the provided human-described date and time and
display the result without actually changing the system clock. (See
parsedate(3) for
examples.)
-
-
- -j
- Parse the provided canonical representation of date and
time (described below) and display the result without actually changing
the system clock.
-
-
- -n
- The utility
timed(8) is used to
synchronize the clocks on groups of machines. By default, if
timed(8) is running,
date will set the time on all of the machines in the
local group. The -n option stops date
from setting the time for other than the current machine.
-
-
- -r
seconds
- Print out the date and time that is
seconds from the Epoch.
-
-
- -u
- Display or set the date in UTC (universal) time.
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
- The first two digits of the year (the century).
- yy
- The second two digits of the year. If
yy is specified, but CC is
not, a value for yy between 69 and 99 results in a
CC value of 19. Otherwise, a
CC value of 20 is used.
- mm
- The month of the year, from 01 to 12.
- dd
- The day of the month, from 01 to 31.
- HH
- The hour of the day, from 00 to 23.
- MM
- The minute of the hour, from 00 to 59.
- SS
- The second of the minute, from 00 to 60.
Everything but the minutes is optional.
Time changes for Daylight Saving and Standard Time and leap seconds and years
are handled automatically.
ENVIRONMENT
The following environment variables affect the execution of
date:
-
-
TZ
- The timezone to use when displaying dates. See
environ(7) for more
information.
FILES
- /etc/localtime
- Symlink pointing to system's default timezone information
file in /usr/share/zoneinfo directory.
- /usr/lib/locale/<L>/LC_TIME
- Description of time locale <L>.
- /usr/share/zoneinfo
- Time zone information directory.
- /usr/share/zoneinfo/posixrules
- Used with POSIX-style TZ's.
- /usr/share/zoneinfo/GMT
- For UTC leap seconds.
- /var/log/wtmp
- A record of date resets and time changes.
- /var/log/messages
- A record of the user setting the time.
If
/usr/share/zoneinfo/GMT is absent, UTC leap seconds are
loaded from
/usr/share/zoneinfo/posixrules.
EXAMPLES
The command:
date '+DATE: %m/%d/%y%nTIME: %H:%M:%S'
will display:
DATE: 11/21/87
TIME: 13:36:16
The command:
sets the date to “
June 13, 1985, 4:27 PM
”.
The command:
sets the time to
2:32 PM
, without modifying the date.
DIAGNOSTICS
Exit status is 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(8) occurs when the
communication between
date and
timed(8) fails.
SEE ALSO
adjtime(2),
gettimeofday(2),
settimeofday(2),
parsedate(3),
strftime(3),
utmp(5),
environ(7),
timed(8)
R. Gusella and S.
Zatti, TSP: The Time Synchronization Protocol for
UNIX 4.3BSD.
STANDARDS
The
date utility is expected to be compatible with
IEEE Std 1003.2 (“POSIX.2”).
HISTORY
A
date utility appeared in
Version 1
AT&T UNIX.