Most restaraunts will end breakfast from 11:00 AM to 1:00 PM.
Technically after 9:00 AM or 10:00 AM and before noon, it's "Brunch".
Though, if you want to get really technical, breakfast is just a word used to describe eating after sleeping, or "Breaking Fast". Fast being an older term meaning you did not eat or drink for a period of time.
I work a night job (11PM to 7 AM), so my "Breakfast" usually happens anywhere from 3-5 PM.