Date in OPDS Feed

Hallo All
I have a problem that the Server/OPDS does not send the date a book was add to calibre to the Device/ Reader SW. Every time I switch devices or Reader SW and load the books they show up with the actuall date I transfered them and not with the date i bought them (or loaded them into calibre). with over 3000 books in my library this is getting quite anoying, as I can not used the sort function "Date added" adequatly)

Please integrate the date added data i th ODPS feed

Thanks a lot
THomas