I think once it shows up, it doesn't change (at least that was the case for me). Although, if you want the build date, talk to your service department after you get the car and they can pull up an OASIS report (I believe that's what it's called) and it has all kinds of information on it (build date, for warranty purposes, I assume; service bulletins; etc). I'm not really sure why it never had a date on the window sticker, but I've seen Fusion stickers before that do have them. When I pick up my car tomorrow, I'm going to see if the sticker is any different than the one online.