What are expiration dates?

The term expiration date is commonly used as a catch-all phrase referring to all product dating, including those labeled “sell by,” “best by, and “use by. ” Some of these dates are recommendations to consumers about how long the product will maintain peak quality. Others are messages to store managers telling them when to take products off the shelves. The word expiration, or an abbreviation for it (exp.), is also used as a specific label to mean that, because of diminished quality and/or safety risks, a particular item shouldn’t be used past the printed date.
Source(s):
USDA Fact Sheets “Food Product Dating”
Consumer Savvy Tips - “What’s the Deal with Expiration Dates?”