Confused By Expiration Dates? You’re Not Alone. Here’s What They Really Mean

Most Americans are needlessly tossing out packaged food—not because it’s gone bad, but because they take the date stamped on it far too literally. That’s according to a recent study published in the journal Waste Management, which surveyed more than 1,000 people about the phrases and dates on food packages.

Many Americans wrongly believed that food product dates—often prefaced by “best by” or “sell by”—are federally regulated and indicate the point after which the food is no longer safe to eat. (Neither is true: labeling decisions are made voluntarily by food companies and are meant to help consumers determine how fresh a food is, according to the USDA.) As a result, 84% of people throw out food when it’s close to the package date at least occasionally, the researchers found.

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The study shows “not only that consumers widely misunderstand current labels, but also that misunderstanding and misplaced trust in the labels lead to excess reported discards,” the authors write.

Here’s what you need to know about food labels and what to toss when.

What are the differences between food date labels?

“Best by” refers to when a food is at peak flavor or quality, says Janell Goodwin, a technical information specialist with the USDA (who was not involved with the study). “Sell by” indicates how long a store should sell or display a product for inventory management reasons. And the “use by” date is the last recommended day that a product can be eaten at peak quality, Goodwin says. “These are all dates of quality and freshness, not of safety,” she says. Yet in the Waste Management study, 42% of people thought “use by” referred to safety, and 19% thought the same of “sell by.”

In an attempt to clear up confusion, some industry groups, including the Grocery Manufacturers Association (GMA) and the Food Marketing Institute, are pushing to narrow the list of food date labels to only two options: “best if used by,” which would relate to freshness and quality, and “use by,” which would refer to the last safe day to eat highly perishable foods. While some food companies now voluntarily follow this two-date system, as far as the federal government is concerned, no date that’s stamped on a package refers to safety.

Should you throw out food past its label date?

There’s no reason to trash something just because the date printed on the package has come and gone, Goodwin says. “If the date passes during home storage, a product should still be safe and wholesome if handled properly until the time of spoilage is evident,” she says. Instead, use your senses: Spoilage bacteria will typically produce a noticeable change in odor, flavor or texture. If none of these have developed, it’s probably safe to keep your food. (You can help protect yourself from bacteria that cause food-borne illnesses, like E. coli and salmonella, by cooking or reheating foods to USDA-recommended temperatures.) The only product with a firm use-by date is infant formula, Goodwin says. Otherwise, you can usually trust your gut over the package date.

Can you freeze food that’s going bad?

Freezing excess food, like meat and bread, is a great way to cut down on waste. If you know you likely won’t use all of something, freeze it sooner rather than later, Goodwin recommends.

“Anything that’s frozen will not spoil, no matter when you freeze it,” Goodwin says. But “the longer you wait to freeze an item, the less the freshness and quality will be” when you defrost it. Frozen food should stay safe indefinitely, but its quality may degrade over time. Find the USDA’s recommended storage times here.

When it is time to defrost, Goodwin says the safest way to do so is by placing food in the refrigerator until it thaws, rather than leaving it out on the counter.

How long does pantry food really last?

In theory, shelf-stable foods like pasta, snack foods, canned goods, baking products and jerky really do last indefinitely, Goodwin says. But that doesn’t mean they’ll taste as they should forever. “It means they will be safe indefinitely,” she says. “However for freshness and quality, it depends on what the product is.” Unopened canned goods may be unaffected for years as long as the packaging is intact, while dried foods like pasta may get stale or change flavor slightly if kept for a long time.

How long can you keep leftovers?

You should be able to see, smell or taste when cooked food has spoiled, Goodwin says. (If you have any doubts, you can consult the USDA’s FoodKeeper app, a comprehensive guide to how long specific foods last.) But she says you should generally throw out leftovers after about four days.

“Spoilage bacteria does grow in the refrigerator,” she says, so even properly stored leftovers won’t last forever.

Write to Jamie Ducharme at jamie.ducharme@time.com.