Do you mean as in the have the document statistics show a future date?
Change your system clock to the future date > open or create the document >
save it > close it > change your clock back
Now if you want it to appear as though it was created all on the same future
date (if it is an existing document), you might need to copy the content over
to a new document and then save while the clock is forward.
Or, you could just type a future date manually in the header/footer ;p
Cheers