A date mark is the date stamped or printed on packaged food to tell the consumer how long it stays at its best or remains safe. Two systems dominate: the use-by date, a safety deadline for highly perishable foods such as chilled meat, dairy, and ready meals — food past this date should not be eaten even if it looks fine; and the best-before date, a quality marker for shelf-stable foods like biscuits, pasta, and canned goods, which may lose crispness or flavour afterwards but remain safe. Manufacturers set the marks from shelf-life testing under realistic storage conditions. The distinction matters for waste as well as safety: confusing the two sends tonnes of safe food to landfill. Regulators require the marks to be legible and honest, and retailers must pull use-by-expired stock from sale.