DATE(P) POSIX Programmer's Manual DATE(P)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
IEEE Std 1003.1-2001, 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 dec‐
imal 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 dec‐
imal 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 dec‐
imal 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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, Section 7.3.5, LC_TIME). If the corresponding
keyword (see era, era_year, era_d_fmt, and alt_digits in the Base Defi‐
nitions volume of IEEE Std 1003.1-2001, Section 7.3.5, LC_TIME) is not
specified or not supported for the current locale, the unmodified con‐
version 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 sym‐
bols.
%OI Hour (12-hour clock) using the locale's alternative numeric sym‐
bols.
%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 IEEE Std 1003.1-2001
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
IEEE Std 1003.1-2001, 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 writ‐
ten 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>s 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
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 pur‐
pose. 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 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 8601:2000 standard
where Monday is the first weekday and the algorithm for the first
week number is more complex: If the week (Monday to Sunday) contain‐
ing 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 specifica‐
tions %u and %V , added as a result of international comments.
FUTURE DIRECTIONS
None.
SEE ALSO
The System Interfaces volume of IEEE Std 1003.1-2001, printf(), strf‐
time()COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 DATE(P)
