I'd be surprised if they actually did anything more than glance at that part of your app. So many other things to look at, and most applicants are around the same age. I bet most PDs don't even glance at the birthdate section. They aren't sorting through apps trying to weed out the people who are older than 30, they are looking at grades and step scores (well, at least pre-pass/fail), USMG status, etc. first.