An expiry date is the last date on which something can be used — the final deadline after which the product should not be consumed or used. The term covers the family of date marks: the use-by date on perishables, a genuine safety limit; the best-before date on shelf-stable foods, a quality marker; and the display-until date, a stock-control tool for retailers. Shoppers often treat them as one, but the distinction is the key to both safety and waste — discarding safe food past its best-before, or risking illness past a use-by. Manufacturers set the dates from shelf-life testing; regulators require them legible and honest. The expiry date is the pack’s contract with time, and reading which kind of date it is decides whether the food is wasted or the eater is endangered.