Provided by: manpages-posix_2013a-2_all bug

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.1‐2008,  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 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.1‐2008, 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 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.1‐2008,  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.

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 Guidelines

       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  Electrical  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 files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .