NAME

DateTime::Format::Excel - Convert between DateTime and Excel dates.

SYNOPSIS

    use DateTime::Format::Excel;

    # From Excel via class method:

    my $datetime = DateTime::Format::Excel->parse_datetime( 37680 );
    print $datetime->ymd();     # prints 2003-02-28

    my $datetime = DateTime::Format::Excel->parse_datetime( 40123.625 );
    print $datetime->iso8601(); # prints 2009-11-06T15:00:00

    #  or via an object
    
    my $excel = DateTime::Format::Excel->new();
    print $excel->parse_datetime( 25569 )->ymd; # prints 1970-01-01

    # Back to Excel number:
    
    use DateTime;
    my $dt = DateTime->new( year => 1979, month => 7, day => 16 );
    my $daynum = DateTime::Format::Excel->format_datetime( $dt );
    print $daynum; # prints 29052

    my $dt_with_time = DateTime->new( year => 2010, month => 7, day => 23
                                    , hour => 18, minute => 20 );
    my $excel_date = DateTime::Format::Excel->format_datetime( $dt_with_time );
    print $excel_date; # prints 40382.763888889

    # or via the object created above
    my $other_daynum = $excel->format_datetime( $dt );
    print $other_daynum; # prints 29052

DESCRIPTION

Excel uses a different system for its dates than most Unix programs. This module allows you to convert between a few of the Excel raw formats and "DateTime" objects, which can then be further converted via any of the other "DateTime::Format::*" modules, or just with "DateTime"'s methods.

If you happen to be dealing with dates between 1 Jan 1900 and 1 Mar 1900 please read the notes on epochs.

Since version 0.30 this modules handles the time part (the decimal fraction of the Excel time number) correctly, so you can convert a single point in time to and from Excel format. (Older versions did only calculate the day number, effectively loosing the time of day information). The H:M:S is stored as a fraction where 1 second = 1 / (60*60*24).

If you're wanting to handle actual spreadsheet files, you may find Spreadsheet::WriteExcel and Spreadsheet::ParseExcel of use.

CONSTRUCTORS

new

Creates a new "DateTime::Format::Excel" instance. This is generally not required for simple operations. If you wish to use a different epoch, however, then you'll need to create an object.

   my $excel = DateTime::Format::Excel->new()
   my $copy = $excel->new();

It takes no parameters. If called on an existing object then it clones the object.

clone

This method is provided For those who prefer to explicitly clone via a method called "clone()". If called as a class method it will die.

   my $clone = $original->clone();

CLASS/OBJECT METHODS

These methods work as both class and object methods.

parse_datetime

Given an Excel day number, return a "DateTime" object representing that date and time.

    # As a class method
    my $datetime = DateTime::format::Excel->parse_datetime( 37680 );
    print $datetime->ymd('.'); # '2003.02.28'

    # Or via an object
    my $excel = DateTime::Format::Excel->new();
    my $viaobj $excel->parse_datetime( 25569 );
    print $viaobj->ymd; # '1970-01-01'

format_datetime

Given a "DateTime" object, return the Excel daynum time.

    use DateTime;
    my $dt = DateTime->new( year => 1979, month => 7, day => 16 );
    my $daynum = DateTime::Format::Excel->format_datetime( $dt );
    print $daynum; # 29052

    # or via an object
    my $excel = DateTime::Format::Excel->new();
    $excel->epoch_mac(); # Let's imagine we want the Mac number
    my $mac_daynum = $excel->format_datetime( $dt );
    print $mac_daynum; # 27590

OBJECT METHODS

epoch

In scalar context, returns a string identifying the current epoch.

   my $epoch = $excel->epoch();

Currently either `mac' or `win' with the default being `win'.

In list context, returns appropriate parameters with which to create a "DateTime" object representing the start of the epoch.

   my $base = DateTime->new( $excel->epoch );

epoch_mac

Set the object to use a Macintosh epoch.

   $excel->epoch_mac(); # epoch is now  1 Jan 1904

Thus, 1 maps to "2 Jan 1904".

epoch_win

Set the object to use a Windows Excel epoch.

   $excel->epoch_win(); # epoch is now 30 Dec 1899

Thus, 2 maps to "1 Jan 1900".

EPOCHS

Excel uses ``number of days since 31 Dec 1899''. Naturally, Microsoft messed this up because they happened to believe that 1900 was a leap year. In this module, we assume what Psion assumed for their Abacus / Sheet program: 1 Jan 1900 maps to 2 rather than 1. Thus, 61 maps to 1 Mar 1900 in both Excel and this module (and Abacus).

Excel for Macintosh has a little option hidden away in its calculations preferences. It can use either the Windows epoch, or it can use the Macintosh epoch, which means that the day number is calculated as ``number of days since 1 Jan 1904''. This module supports both notations.

Note: the results of this module have only been compared with Microsoft Excel for Macintosh 98 and Abacus on the Acorn Pocket Book. Where they have differed, I've opted for Abacus's result rather than Excel's.

THANKS

Dave Rolsky (DROLSKY) for kickstarting the DateTime project.

SUPPORT

Support for this module is provided via the datetime@perl.org email list. See http://lists.perl.org/ for more details.

Alternatively, log them via the CPAN RT system via the web or email:

    http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DateTime%3A%3AFormat%3A%3AExcel
    bug-datetime-format-excel@rt.cpan.org

This makes it much easier for us to track things and thus means your problem is less likely to be neglected.

LICENCE AND COPYRIGHT

The full text of the licences can be found in the Artistic and COPYING files included with this module.

AUTHOR

Originally written by Iain Truskett <spoon@cpan.org>, who died on December 29, 2003.

Maintained by Dave Rolsky <autarch@urth.org> and, since 2010-06-01, by Achim Bursian <aburs@cpan.org>.

The following people have either submitted patches or suggestions, or their bug reports or comments have inspired the appropriate patches.

 Peter (Stig) Edwards  
 Bobby Metz