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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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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.1‐2017, 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.
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.)
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.1‐2017, 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.
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.1‐2017, 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(3p),
strftime(3p)
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 .
IEEE/The Open Group 2017 DATE(1P)
Pages that refer to this page: ar(1p), touch(1p)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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