Does this sound familiar? You grab a container of yogurt from the fridge that has been hanging around for who knows how long, take off the lid and look for any signs of fuzzy growing things and say, "Honey, smell this and tell me if it's still good."
This probably is not the best way of checking for freshness. The best way is a voluntary system of labeling - yes, voluntary. Although they are not required by federal law (except for infant formula and baby food), just about every item a grocery store sells is marked with some sort of date. State laws vary, but most states require that dairy items be pulled from store shelves on their expiration date.