When you clean out your fridge or pantry, some things obviously need to go. That old cheese that's sprouted a greenish-black tuft of hair? That ancient container of broccoli that smells like something you'd rather not describe — or ever smell again? Those clearly belong in the garbage can — outside — several yards away.

But what about the foods that look and smell fine, but have "sell-by," "use-by," "best-by," "best-before" or "enjoy-by" dates that have come and gone? You should probably pitch those, too, right?

Not so fast. While most of us probably treat the dates on our food packaging as gospel, they are, it turns out, highly unreliable indicators of freshness. "Basically made up," Smithsonian Magazine says. "Unclear" and "useless," the Washington Post sniffs. "Inconsistent and confusing," Climate Progress notes.

In a report released in September 2013 by the Harvard Food Law and Policy Clinic and the Natural Resources Defense Council, "The Dating Game: How Confusing Food Date Labels Lead to Food Waste in America," the authors point out that dates on food labels that purport to tell us whether its contents are fresh, or — uh — not so fresh, are "surprisingly under-regulated."

Federal food-dating standards are sparse — dating is mandated only on infant formula — and state and local laws vary. For instance, only some states require that perishable foods like milk be sold prior to their expiration dates. As a consequence, labeling practices are wildly inconsistent and consumers cannot rely on them — and amidst this confusion, a lot of people throw away an awful lot of perfectly good food.

The authors of the Harvard/NRDC report have called for clearer standards and greater regulation, but in the meantime, how are you to know when to throw out your food and when to keep it around?

The website Eat By Date provides helpful information on the shelf lives of perishables, including dairy products, drinks, fruits, vegetables, grains and proteins. Food Network's Healthy Eats blog also offers guidance. And you can always just follow your nose.