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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of
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NAME
date — write the date and time
SYNOPSIS
date [-u] [+format]
date [-u] mmddhhmm[[cc]yy]
DESCRIPTION
The date utility shall write the date and time to standard output or attempt to set the
system date and time. By default, the current date and time shall be written. If an
operand beginning with '+' is specified, the output format of date shall be controlled by
the conversion specifications and other text in the operand.
OPTIONS
The date utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section
12.2, Utility Syntax Guidelines.
The following option shall be supported:
-u Perform operations as if the TZ environment variable was set to the string
"UTC0", or its equivalent historical value of "GMT0". Otherwise, date shall use
the timezone indicated by the TZ environment variable or the system default if
that variable is unset or null.
OPERANDS
The following operands shall be supported:
+format When the format is specified, each conversion specifier shall be replaced in the
standard output by its corresponding value. All other characters shall be copied
to the output without change. The output shall always be terminated with a
<newline>.
Conversion Specifications
%a Locale's abbreviated weekday name.
%A Locale's full weekday name.
%b Locale's abbreviated month name.
%B Locale's full month name.
%c Locale's appropriate date and time representation.
%C Century (a year divided by 100 and truncated to an integer) as a decimal
number [00,99].
%d Day of the month as a decimal number [01,31].
%D Date in the format mm/dd/yy.
%e Day of the month as a decimal number [1,31] in a two-digit field with
leading <space> character fill.
%h A synonym for %b.
%H Hour (24-hour clock) as a decimal number [00,23].
%I Hour (12-hour clock) as a decimal number [01,12].
%j Day of the year as a decimal number [001,366].
%m Month as a decimal number [01,12].
%M Minute as a decimal number [00,59].
%n A <newline>.
%p Locale's equivalent of either AM or PM.
%r 12-hour clock time [01,12] using the AM/PM notation; in the POSIX
locale, this shall be equivalent to %I:%M:%S %p.
%S Seconds as a decimal number [00,60].
%t A <tab>.
%T 24-hour clock time [00,23] in the format HH:MM:SS.
%u Weekday as a decimal number [1,7] (1=Monday).
%U Week of the year (Sunday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the first Sunday shall
be considered to be in week 0.
%V Week of the year (Monday as the first day of the week) as a decimal
number [01,53]. If the week containing January 1 has four or more days
in the new year, then it shall be considered week 1; otherwise, it shall
be the last week of the previous year, and the next week shall be week
1.
%w Weekday as a decimal number [0,6] (0=Sunday).
%W Week of the year (Monday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the first Monday shall
be considered to be in week 0.
%x Locale's appropriate date representation.
%X Locale's appropriate time representation.
%y Year within century [00,99].
%Y Year with century as a decimal number.
%Z Timezone name, or no characters if no timezone is determinable.
%% A <percent-sign> character.
See the Base Definitions volume of POSIX.1‐2017, Section 7.3.5, LC_TIME for the
conversion specifier values in the POSIX locale.
Modified Conversion Specifications
Some conversion specifiers can be modified by the E and O modifier characters to indicate
a different format or specification as specified in the LC_TIME locale description (see
the Base Definitions volume of POSIX.1‐2017, Section 7.3.5, LC_TIME). If the
corresponding keyword (see era, era_year, era_d_fmt, and alt_digits in the Base
Definitions volume of POSIX.1‐2017, Section 7.3.5, LC_TIME) is not specified or not
supported for the current locale, the unmodified conversion specifier value shall be used.
%Ec Locale's alternative appropriate date and time representation.
%EC The name of the base year (period) in the locale's alternative representation.
%Ex Locale's alternative date representation.
%EX Locale's alternative time representation.
%Ey Offset from %EC (year only) in the locale's alternative representation.
%EY Full alternative year representation.
%Od Day of month using the locale's alternative numeric symbols.
%Oe Day of month using the locale's alternative numeric symbols.
%OH Hour (24-hour clock) using the locale's alternative numeric symbols.
%OI Hour (12-hour clock) using the locale's alternative numeric symbols.
%Om Month using the locale's alternative numeric symbols.
%OM Minutes using the locale's alternative numeric symbols.
%OS Seconds using the locale's alternative numeric symbols.
%Ou Weekday as a number in the locale's alternative representation (Monday = 1).
%OU Week number of the year (Sunday as the first day of the week) using the locale's
alternative numeric symbols.
%OV Week number of the year (Monday as the first day of the week, rules corresponding
to %V), using the locale's alternative numeric symbols.
%Ow Weekday as a number in the locale's alternative representation (Sunday = 0).
%OW Week number of the year (Monday as the first day of the week) using the locale's
alternative numeric symbols.
%Oy Year (offset from %C) in alternative representation.
mmddhhmm[[cc]yy]
Attempt to set the system date and time from the value given in the operand.
This is only possible if the user has appropriate privileges and the system
permits the setting of the system date and time. The first mm is the month
(number); dd is the day (number); hh is the hour (number, 24-hour system); the
second mm is the minute (number); cc is the century and is the first two digits
of the year (this is optional); yy is the last two digits of the year and is
optional. If century 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 current year is the default if yy is
omitted.
Note: It is expected that in a future version of this standard the default
century inferred from a 2-digit year will change. (This would apply to
all commands accepting a 2-digit year as input.)
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of date:
LANG Provide a default value for the internationalization variables that are unset or
null. (See the Base Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables for the precedence of internationalization
variables used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other
internationalization variables.
LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data
as characters (for example, single-byte as opposed to multi-byte characters in
arguments).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of
diagnostic messages written to standard error.
LC_TIME Determine the format and contents of date and time strings written by date.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
TZ Determine the timezone in which the time and date are written, unless the -u
option is specified. If the TZ variable is unset or null and -u is not
specified, an unspecified system default timezone is used.
ASYNCHRONOUS EVENTS
Default.
STDOUT
When no formatting operand is specified, the output in the POSIX locale shall be
equivalent to specifying:
date "+%a %b %e %H:%M:%S %Z %Y"
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 The date was written successfully.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
Conversion specifiers are of unspecified format when not in the POSIX locale. Some of them
can contain <newline> characters in some locales, so it may be difficult to use the format
shown in standard output for parsing the output of date in those locales.
The range of values for %S extends from 0 to 60 seconds to accommodate the occasional leap
second.
Although certain of the conversion specifiers in the POSIX locale (such as the name of the
month) are shown with initial capital letters, this need not be the case in other locales.
Programs using these fields may need to adjust the capitalization if the output is going
to be used at the beginning of a sentence.
The date string formatting capabilities are intended for use in Gregorian-style calendars,
possibly with a different starting year (or years). The %x and %c conversion
specifications, however, are intended for local representation; these may be based on a
different, non-Gregorian calendar.
The %C conversion specification was introduced to allow a fallback for the %EC
(alternative year format base year); it can be viewed as the base of the current
subdivision in the Gregorian calendar. The century number is calculated as the year
divided by 100 and truncated to an integer; it should not be confused with the use of
ordinal numbers for centuries (for example, ``twenty-first century''.) Both the %Ey and %y
can then be viewed as the offset from %EC and %C, respectively.
The E and O modifiers modify the traditional conversion specifiers, so that they can
always be used, even if the implementation (or the current locale) does not support the
modifier.
The E modifier supports alternative date formats, such as the Japanese Emperor's Era, as
long as these are based on the Gregorian calendar system. Extending the E modifiers to
other date elements may provide an implementation-defined extension capable of supporting
other calendar systems, especially in combination with the O modifier.
The O modifier supports time and date formats using the locale's alternative numerical
symbols, such as Kanji or Hindi digits or ordinal number representation.
Non-European locales, whether they use Latin digits in computational items or not, often
have local forms of the digits for use in date formats. This is not totally unknown even
in Europe; a variant of dates uses Roman numerals for the months: the third day of
September 1991 would be written as 3.IX.1991. In Japan, Kanji digits are regularly used
for dates; in Arabic-speaking countries, Hindi digits are used. The %d, %e, %H, %I, %m,
%S, %U, %w, %W, and %y conversion specifications always return the date and time field in
Latin digits (that is, 0 to 9). The %O modifier was introduced to support the use for
display purposes of non-Latin digits. In the LC_TIME category in localedef, the optional
alt_digits keyword is intended for this purpose. As an example, assume the following
(partial) localedef source:
alt_digits "";"I";"II";"III";"IV";"V";"VI";"VII";"VIII" \
"IX";"X";"XI";"XII"
d_fmt "%e.%Om.%Y"
With the above date, the command:
date "+%x"
would yield 3.IX.1991. With the same d_fmt, but without the alt_digits, the command would
yield 3.9.1991.
EXAMPLES
1. The following are input/output examples of date used at arbitrary times in the POSIX
locale:
$ date
Tue Jun 26 09:58:10 PDT 1990
$ date "+DATE: %m/%d/%y%nTIME: %H:%M:%S"
DATE: 11/02/91
TIME: 13:36:16
$ date "+TIME: %r"
TIME: 01:36:32 PM
2. Examples for Denmark, where the default date and time format is %a %d %b %Y %T %Z:
$ LANG=da_DK.iso_8859-1 date
ons 02 okt 1991 15:03:32 CET
$ LANG=da_DK.iso_8859-1 \
date "+DATO: %A den %e. %B %Y%nKLOKKEN: %H:%M:%S"
DATO: onsdag den 2. oktober 1991
KLOKKEN: 15:03:56
3. Examples for Germany, where the default date and time format is %a %d.%h.%Y, %T %Z:
$ LANG=De_DE.88591 date
Mi 02.Okt.1991, 15:01:21 MEZ
$ LANG=De_DE.88591 date "+DATUM: %A, %d. %B %Y%nZEIT: %H:%M:%S"
DATUM: Mittwoch, 02. Oktober 1991
ZEIT: 15:02:02
4. Examples for France, where the default date and time format is %a %d %h %Y %Z %T:
$ LANG=Fr_FR.88591 date
Mer 02 oct 1991 MET 15:03:32
$ LANG=Fr_FR.88591 date "+JOUR: %A %d %B %Y%nHEURE: %H:%M:%S"
JOUR: Mercredi 02 octobre 1991
HEURE: 15:03:56
RATIONALE
Some of the new options for formatting are from the ISO C standard. The -u option was
introduced to allow portable access to Coordinated Universal Time (UTC). The string
"GMT0" is allowed as an equivalent TZ value to be compatible with all of the systems using
the BSD implementation, where this option originated.
The %e format conversion specification (adopted from System V) was added because the ISO C
standard conversion specifications did not provide any way to produce the historical
default date output during the first nine days of any month.
There are two varieties of day and week numbering supported (in addition to any others
created with the locale-dependent %E and %O modifier characters):
* The historical variety in which Sunday is the first day of the week and the weekdays
preceding the first Sunday of the year are considered week 0. These are represented by
%w and %U. A variant of this is %W, using Monday as the first day of the week, but
still referring to week 0. This view of the calendar was retained because so many
historical applications depend on it and the ISO C standard strftime() function, on
which many date implementations are based, was defined in this way.
* The international standard, based on the ISO 8601:2004 standard where Monday is the
first weekday and the algorithm for the first week number is more complex: If the week
(Monday to Sunday) containing January 1 has four or more days in the new year, then it
is week 1; otherwise, it is week 53 of the previous year, and the next week is week 1.
These are represented by the new conversion specifications %u and %V, added as a
result of international comments.
FUTURE DIRECTIONS
None.
SEE ALSO
The Base Definitions volume of POSIX.1‐2017, Section 7.3.5, LC_TIME, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2017, fprintf(), strftime()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have
been introduced during the conversion of the source files to man page format. To report
such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .