How Does Food Manufactuers know the expiry date of Food Products?!
Answers: They do it via several tests and experiments. They also apply different amounts of preservitives to see whether it makes them taste any different or it spoils the food. Also you shouldn't run by just the used by date, you should always use your smell and taste because they always over estimate to be safe.
through testings.
What is the F.D.A. ?
yes its by their Quality control inspectors who re-set the machines to date the items
by knowing how much preservative added in the food products