There is no way that I know of to change the date field on the T1. It is set by the reader to the date the book is put on the reader.
You can create a special collection containing all books, sorted by whatever metadata you want. See paragraph number 5 in the first post of
this thread. You should be able to use "abs:pubdate", which you enter in the collections box of the Sony PRST1 device plugin (preferences -> plugins -> device interface plugins -> SONY PRST1).
On the T1, to see books in the collection in pubdate order, you must select the sort "added order".