Hi Jeff,
internally DocuWare always stores date in the same format, only the representation is defined on UI level. So every user can decide, in which format he/she wants to see the date. This setting is then also applied to stamps.
Additionally there is a default setting for the whole organization, this is e.g. used if an email is sent out which includes a date. I think in your case it would be beneficial to use a date format which is recognized in both countries (e.g. YYYY-MM-DD).
Depending on the type of documents there are also different options to recognize the date on the document.
Regards
Tobias Getz