NAME
    Date::ISO - Perl extension for converting dates between ISO and
    Gregorian formats.

SYNOPSIS
      use Date::ISO;
      ($yearnumber, $weeknumber, $weekday) = iso($year, $month, $day);

    Note that year and month here are as given by localtime, not as given by
    a calendar. Hence, January 1, 2001 is (101, 0, 1). This is probably
    undesired behavior, and may be changed in a future release.

      ($yearnumber, $weeknumber, $weekday) = localiso(time);
      ($year, $month, $day) = inverseiso($iso_year, $iso_week, $iso_week_day);

    Or, using the object interface:

      use Date::ISO qw();
      my $iso = Date::ISO->new( ISO => $iso_date_string );

      $iso_year = $iso->iso_year;
      $year = $iso->year;

      $iso_week = $iso->iso_week;
      $week_day = $iso->iso_week_day;

      $month = $iso->month;
      $day = $iso->day;

DESCRIPTION
    Convert dates between ISO and Gregorian formats.

  iso

            ($year, $week, $day) = iso($year, $month, $day);
        ($year, $week, $day) = iso(2001, 4, 28); # April 28, 2001

    Returns the ISO year, week, and day of week, when given the (Gregorian)
    year, month, and day.

    Note that years are full 4 digit years, and months are numbered with
    January being 1.

  inverseiso

            ($year, $month, $day) = inverseiso($year, $week, $day);

    Given an ISO year, week, and day, returns year, month, and day, as
    localtime would give them to you.

  localiso

            ($year, $week, $day) = localiso(time);

    Given a time value (epoch time) returns the ISO year, week, and day.

OO interface
    The OO interface allows you to create a date object, and determime from
    it the various attributes in the ISO calendar (the year, week, and day
    of that week) and in the Gregorian reckoning (the year, month, and day).

  new

        my $iso = Date::ISO->new( ISO => $iso_date_string );

    or ...

        my $iso = Date::ISO->new( EPOCH = $epoch_time );

    Accepted ISO date string formats are:

        1997-02-05 (Feb 5, 1997)
        19970205 (Same)
        199702 (February 1997)
        1997-W06 (6th week, 1997)
        1997W06 (Same)
        1997-W06-2 (6th week, 2nd day)
        1997W062 (Same as above)
        1997-035 (35th day of 1997)
        1997035 (Same as above)

    2-digit representations of the year are not supported at this time.

    Time values are not supported at this time.

AUTHOR
    Rich Bowen (rbowen@rcbowen.com)

DATE
    $Date: 2001/05/01 23:15:45 $

Additional comments
    For more information about this calendar, please see:

    http://personal.ecu.edu/mccartyr/ISOwdALG.txt

    http://personal.ecu.edu/mccartyr/isowdcal.html

    http://www.cl.cam.ac.uk/~mgk25/iso-time.html

To Do
    Need to flesh out test suite some more. Particularly need to test some
    dates immediately before and after the first day of the year - days in
    which you might be in a different Gregorian and ISO years.

    ISO date format also supports a variety of time formats. I suppose I
    should accept those as valid arguments.

    Need methods to output epoch time, and a variety of valid ISO date
    strings, from a Date::ISO object.

Version History
        
        Revision 1.17  2001/04/30 13:23:35  rbowen
        Removed AutoLoader from ISA, since it really isn't.

        Revision 1.16  2001/04/29 21:31:04  rbowen
        Added new tests, and fixed a lot of bugs in the process. Apparently the
        inverseiso function had never actually worked, and various other functions
        had some off-by-one problems.

        Revision 1.15  2001/04/29 02:42:03  rbowen
        New Tests.
        Updated MANIFEST, Readme for new files, functionality
        Fixed CVS version number in ISO.pm

        Revision 1.14  2001/04/29 02:36:50  rbowen
        Added OO interface.
        Changed functions to accept 4-digit years and 1-based months.