Food dating is not a US federal law, except for infant formula and baby foods. Freshness dating and the terms used are voluntary by manufacturers, except for dairy foods and meat in some states.
The butcher uses a Sell-By date provided by the supplier.
Sell-by dates are on the packaging delivered to the store.
Best-Before dates mean fresh, the product, eaten after the date will be past prime condition.
A Use-By date means DO NOT consume after this date. Rigorous tests by health authorities establish the Use-By date of food sold by butchers.