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DATE(1P) POSIX Programmer's Manual DATE(1P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
date — write the date and time
date [−u] [+format]
date [−u] mmddhhmm[[cc]yy]
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.
The date utility shall conform to the Base Definitions volume of
POSIX.1‐2008, 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.
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.1‐2008, 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.1‐2008, 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.1‐2008, 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.)
Not used.
None.
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.1‐2008, 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.
Default.
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"
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 The date was written successfully.
>0 An error occurred.
Default.
The following sections are informative.
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.
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
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.
None.
The Base Definitions volume of POSIX.1‐2008, Section 7.3.5, LC_TIME,
Chapter 8, Environment Variables, Section 12.2, Utility Syntax
Guidelines
The System Interfaces volume of POSIX.1‐2008, fprintf(3p),
strftime(3p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 .
IEEE/The Open Group 2013 DATE(1P)
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