in advance of course, in anticipation of patrons buying them. But during slow periods of the day up to 80% of the prepared food isn't sold within the 15 minutes or so that it is considered "fresh". This food is thrown out and put in a heavily fortified, locked up dumpster area behind the store, to keep people from "dumpster diving".
Personally, I consider a 15 minute old hamburger to be perfectly edible, even if not sellable. And its incredible to me to think that 4 out of every five hamburgers produced during these slow periods, end up in that locked dumpster and headed to a landfill, rather than being available for a hungry person to eat.