DATE(1P) POSIX Programmer's Manual DATE(1P)PROLOG
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NAMEdate — write the date and time
SYNOPSISdate [−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 speci‐
fied, 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.1‐2008, 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.
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 con‐
taining 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 repre‐
sentation.
%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 appro‐
priate 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 vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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 writ‐
ten, 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 Grego‐
rian-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-Grego‐
rian 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 cur‐
rent 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 alter‐
native numerical symbols, such as Kanji or Hindi digits or ordinal num‐
ber 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 for‐
mats. 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 specifica‐
tions 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 exam‐
ple, 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 Uni‐
versal Time (UTC). The string "GMT0" is allowed as an equivalent TZ
value to be compatible with all of the systems using the BSD implemen‐
tation, where this option originated.
The %e format conversion specification (adopted from System V) was
added because the ISO C standard conversion specifications did not pro‐
vide 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 addi‐
tion 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 consid‐
ered 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 refer‐
ring 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) con‐
taining 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 speci‐
fications %u and %V, added as a result of international comments.
FUTURE DIRECTIONS
None.
SEE ALSO
The Base Definitions volume of POSIX.1‐2008, Section 7.3.5, LC_TIME,
Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guide‐
lines
The System Interfaces volume of POSIX.1‐2008, fprintf(), strftime()COPYRIGHT
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 Electri‐
cal 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
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IEEE/The Open Group 2013 DATE(1P)
