Originally Posted by WillCAD

That's not universal, though. None of the BKs I know of in my part of the country serve breakfast food and lunch food at the same time. Breakfast is served from opening until 10:30 or 11:00, and lunch thereafter. There is generally about a 15-minute period after the switchover where you can buy leftover breakfast food, if they have any.

It might be more common in other parts of the country. I'm only familiar with the southeast.