I've had a fair bit of success just diving into the (well commented) perl code and changing stuff to see what happens.  

I would suggest changing line 101 of perllib/classify/DateList.pm from

     my $date = $doc_obj->get_metadata_element ($doc_obj->get_top_section(), 'Date');

to

    my $date = $doc_obj->get_metadata_element ($doc_obj->get_top_section(), 'dc.Date');

I am not a developer, but I think this would probably work.  

s.

>_________________________________________________
>Stephen De Gabrielle
>Digitisation Officer
>AraDA Project
>
>Northern Territory University Library
>http://www.ntu.edu.au/library
>Tel: (08) 8946 7009 from overseas: 61 8 8946 7009
>Postal address: P.O.Box 41246, Casuarina, NT, 0811, Australia
>CRICOS Provider No: 00300K

>
>Michael Dewsnip <mdewsnip@cs.waikato.ac.nz>
>Sent by: greenstone-users-bounces@list.scms.waikato.ac.nz
>15/09/2003 02:13 PM ZE12
>
> To: "Dwyer, Benjamin J" <benjamin.dwyer@education.tas.gov.au>
> cc: greenstone-users@list.scms.waikato.ac.nz
> bcc:
> Subject: Re: [greenstone-users] DateList Classifier
>
>
>

>Hi Ben,
>
>According to the DateList.pm module (in perllib/classify), the correct format for the dates is yyyymmdd (ie. the second variant you tried).
>
>I think the problem is that DateList assumes that the date metadata is stored in the Date element (not dc.Date) -- and there is no option to change this. I'll add this option to my "to do" list, but for now you can either:
>
>- Assign your date metadata to the Date element (you might have to create this element in the Metadata Set Editor), instead of dc.Date.
>- Edit the DateList.pm file, and change the 'Date' on line 101 to 'dc.Date'.
>
>Hope this helps.
>
>Regards,
>
>Michael
>  
>  
>
>"Dwyer, Benjamin J" wrote:
>
>Hi,
>
>I'm having trouble getting the DateList Classifier to work using the Librarian interface.
>I've created a collection using HTMLPlug, and have given each .html file date metadata in the form of dc.Date.
>I can successfully create a searchable index using dc.Date metadata, however cannot create a Date List classifier.
>I have tried the following date formats: 1900, 19000101, 1900-01-01
>Can anyone help?
>
>Regards,
>
>Ben Dwyer
>
>Service Tasmania Online
>State Library of Tasmania
>
>
>