[gutvol-d] Metadata for original publication date?

Hi, I've not found the right way to include the date of the original publication in e-book metadata, particularly in EPUB books. The Dublin Core has lots of other dates, but they're thinking in terms of updates to modern documents, not a re-published historical document. Of course, to a user, the original publication date of the historical documents of Project Gutenberg is likely to be of greater importance than the most recent publication date. Any ideas?