The date utility writes the date and time to standard output or attempts to set the system date and time. By default, the current date and time will be written.

Specifications of native language translations of month and weekday names are supported. The month and weekday names used for a language are based on the locale specified by the environment variable LC_TIME; see environ(5).

The following is the default form for the "C" locale:

%a %b %e %T %Z %Y

Fri Dec 23 10:10:42 EST 1988

The following options are supported:

-a [-]sss.fff

Slowly adjust the time by sss.fff seconds (fff represents fractions of a second). This adjustment can be positive or negative. The system's clock will be sped up or slowed down until it has drifted by the number of seconds specified. Only the super-user may adjust the time.

-u

Display (or set) the date in Greenwich Mean Time (GMT--universal time), bypassing the normal conversion to (or from) local time.

The following operands are supported:

+format

If the argument begins with +, the output of date is the result of passing format and the current time to strftime(). date uses the conversion specifications listed on the strftime(3C) manual page, with the conversion specification for %C determined by whether /usr/bin/date or /usr/xpg4/bin/date is used:

/usr/bin/date

Locale's date and time representation. This is the default output for date.

/usr/xpg4/bin/date

Century (a year divided by 100 and truncated to an integer) as a decimal number [00-99].

The string is always terminated with a NEWLINE. An argument containing blanks must be quoted; see the EXAMPLES section.

mm

Month number

dd

Day number in the month

HH

Hour number (24 hour system)

MM

Minute number

SS

Second number

cc

Century (a year divided by 100 and truncated to an integer) as a decimal number [00-99]. For example, cc is 19 for the year 1988 and 20 for the year 2007.

yy

Last two digits of the year number. If century (cc) is not specified, then values in the range 69-99 shall refer to years 1969 to 1999 inclusive, and values in the range 00-68 shall refer to years 2000 to 2068, inclusive.

The month, day, year number, and century may be omitted; the current values are applied as defaults. For example, the following entry:

example% date 10080045

sets the date to Oct 8, 12:45 a.m. The current year is the default because no year is supplied. The system operates in GMT. date takes care of the conversion to and from local standard and daylight time. Only the super-user may change the date. After successfully setting the date and time, date displays the new date according to the default format. The date command uses TZ to determine the correct time zone information; see environ(5).

See environ(5) for descriptions of the following environment variables that affect the execution of date: LC_CTYPE, LC_TIME, LC_MESSAGES, and NLSPATH.

TZ

Determine the timezone in which the time and date are written, unless the -u option is specified. If the TZ variable is not set and the -u is not specified, the system default timezone is used.

The following exit values are returned:

0

Successful completion.

>0

An error occurred.

See attributes(5) for descriptions of the following attributes:

/usr/bin/date

/usr/xpg4/bin/date

strftime(3C), attributes(5), environ(5), XPG4(5)

no permission

You are not the super-user and you tried to change the date.

bad conversion

The date set is syntactically incorrect.

If you attempt to set the current date to one of the dates that the standard and alternate time zones change (for example, the date that daylight time is starting or ending), and you attempt to set the time to a time in the interval between the end of standard time and the beginning of the alternate time (or the end of the alternate time and the beginning of standard time), the results are unpredictable.

Using the date command from within windowing environments to change the date can lead to unpredictable results and is unsafe. It may also be unsafe in the multi-user mode, that is, outside of a windowing system, if the date is changed rapidly back and forth. The recommended method of changing the date is 'date -a'.