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DATE(1) General Commands Manual DATE(1)

date —
display or set date and time

date [-aju] [-d dst] [-r seconds] [-t minutes_west] [-z output_zone] [+format] [[[[[[cc]yy]mm]dd]HH]MM[.SS]]

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.

Changing the system date has some risks, as described in settimeofday(2). Only the superuser may change the date.

The options are as follows:

Use the adjtime(2) call to gradually skew the local time to the desired time rather than just hopping.
dst
Set the system's value for Daylight Saving Time. If dst is non-zero, future calls to gettimeofday(2) will return a non-zero value for tz_dsttime.
Parse the provided date and time and display the result without changing the clock.
seconds
Print out (in specified format) the date and time represented by seconds from the Epoch.
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).
Display or set the date in UTC (Coordinated Universal) time.
output_zone
Just before printing the time, change to the specified timezone; see the description of TZ below. This can be used with -j to easily convert time specifications from one zone to another.

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:

%a %b %e %H:%M:%S %Z %Y

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:

ccyy
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
Month: a number from 1 to 12.
dd
Day: a number from 1 to 31.
HH
Hour: a number from 0 to 23.
MM
Minute: a number from 0 to 59.
SS
Second: a number from 0 to 60 (permitting a leap second), preceded by a period.

Everything but the minute is optional.

Time changes for Daylight Saving Time, standard time, leap seconds, and leap years are handled automatically.

The time zone to use when parsing or displaying dates. See environ(7) for more information. If this variable is not set, the time zone is determined based on /etc/localtime, which the administrator adjusts using the -l option of zic(8).

/var/log/wtmp
record of date resets and time changes
/var/log/messages
record of the user setting the time

The date utility exits 0 on success, and >0 if an error occurs.

Display the date using the specified format string: 
$ date "+DATE: %Y-%m-%d%nTIME: %H:%M:%S"
DATE: 1987-11-21
TIME: 13:36:16

Set the date to June 13, 1985, 4:27 PM:

# date 198506131627

Set the time to 2:32 PM, without modifying the date:

# date 1432

adjtime(2), gettimeofday(2), strftime(3), utmp(5), ntpd(8), rdate(8)

The date utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.

The flags [-adjrtz], as well as the conversion specifiers ‘%F’, ‘%G’, ‘%g’, ‘%k’, ‘%l’, ‘%R’, ‘%s’, ‘%v’, and ‘%+’, are extensions to that specification.

This implementation requires the traditional BSD date format, [[[[[cc]yy]mm]dd]HH]MM[.SS], which differs from the X/Open System Interfaces option of the IEEE Std 1003.1-2008 (“POSIX.1”) specification.

A date command appeared in Version 1 AT&T UNIX.
September 12, 2016 OpenBSD-6.1