# date

## PROLOG



           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.
    


## NAME



           date — write the date and time
    


## SYNOPSIS



           date **[** -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 specified, 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.1‐2017, _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.
    


## 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
                             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.)
    


## 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 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.
    


## 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
           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.
    


## 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 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.
    


## FUTURE DIRECTIONS



           None.
    


* * *