You don’t have to care what the date format looks like on your screen, as long the date is stored in a NotesDateTime field. When it’s in a NotesDateTime field, it has no format, it just has the correct value. From that field you can always extract and display it to any format needed, although ISO 9001 (YYYY-MM-DD HH:mm:SS) is the only one people should use since it’s the best!
Subject: RE: Format of Date changes datatype in LS?
How do you pass it to the mainframe? If you send it via ftp in a text file, it is text even if it is formatted like a date. Same goes for reverse webservices or http pushes.
I think the only way when the date is sent as a Date Type field would be if your mainframe was running on Domino and you send a mail or write a document directly into a database on the mainframe. There might be also some ODBC/COM/OLE interfaces which allow you to send data directly to the mainframe.