Slate says Expiration dates mean very little "Not only are expiration dates misleading, but there's no uniformity in their inaccuracy. Some manufacturers prefer the elusive 'Best if used by,' others opt for the imperative 'Use by,' and then there are those who litter their goods with the most unhelpful 'Sell by' stamps. (I'm happy my bodega owner is clear on when to dump, but what about me?) Such disparities are a consequence of the fact that, with the exception of infant formula and some baby foods, package dates are unregulated by the federal government. And while some states do exercise oversight, there's no standardization. A handful of states, including Massachusetts and West Virginia, and Washington, D.C., require dating of some form for perishable foods. Twenty states insist on dating for milk products, but each has distinct regulations. Milk heading for consumers in Connecticut must bear a 'Sell by' date not more than 12 days from the day of pasteurization. Dairies serving Pennsylvania must conform to 14 days. "