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 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.
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>.
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 IEEE Std 1003.1-2001, Section
7.3.5, LC_TIME for the conversion specifier values in the POSIX locale.
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 Definitions 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 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 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.)
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 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.
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 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:
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 8601:2000 standard where
Monday is the first weekday and the algorithm for the
first week number is more complex: If the week (Monday to Sunday)
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.
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
DATE (P)
2003
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