The dates that matter, and the dates that don't.
Ready to get in on a little secret that food manufacturers don't want you to know? Expiration dates are pretty much BS (though there are some exceptions, as you'll read below).
Many people assume the government oversees those dates, and that's just not true, says Dana Gunders, a senior scientist and lead food waste expert for the Natural Resources Defense Council and author of Waste-Free Kitchen Handbook. In fact, "the only product that has federal regulation is infant formula," she says. (See also: The Grocery Industry Is Urging Food Manufacturers to Adopt Standard Expiration Dates)
So where do the dates come from, then? The manufacturers themselves. They're a guestimate for when the product will be at its peak quality and aren't tied to food safety, Gunders says. For example, yogurt that's past its "expiration" date might be more watery on the top, which makes it slightly less appetizing but not unsafe. Pasteurized food will never go bad, Gunders says.
Food has the potential to make you sick when it's contaminated, not because it's old. "Things like salmonella and E. coli, those are pathogens that get on the food before the food gets to you, and they would make you sick whether or not the food were old," Gunders says. Rather than getting hung up on dates, it's more important to handle and store your food properly, Gunders says. So maybe don't leave chicken salad in a hot car for two hours and then dig in.
The words listed before the date serve as a good hint as to whether you should pay attention to it or if you can be a little more lax. In general, "use by" and "expiration" are on the strictest end of the spectrum, says Mindy Costello, a consumer information specialist with NSF International. "Use by" is usually found on fresh foods like dairy products, meat, and packages of lettuce and other produce. "Expiration" is the one found on baby formulas, though some states also list it on eggs. Even if you decide to ignore all other dates, these are the ones to pay attention to. Though there are some exceptions. Eggs, for instance, can be fine to eat up to five weeks after you purchase them, even if that's a couple of weeks past the date on the carton.
Other language surrounding dates is vaguer (and okay to ignore). First, don't worry about "sell by" dates. They're intended to help stores know how long to display a product, Costello says. "Best by" dates, on the other hand, refer to how long an unopened product will remain fresh, Costello says. "Best by" dates—sometimes listed as "best before," "best if used by," and "durable life date"—are totally fine to consume past that date (because, let's be real, eating a few stale Wheat Thins won't kill you).
If the nitty-gritty code behind all of those terms just isn't sticking, pay attention to the categories of food products instead. "The shorthand I usually give people is that foods they tell pregnant women to avoid are good foods to pay attention to the date," Gunders says. That includes deli meat, unpasteurized dairy products, pre-packaged sandwiches, and hot dogs and sausages that are not fully cooked. All of these have a high risk of being contaminated with listeria, which can multiply even during refrigeration.
As for the rest? "Most foods are fine to eat well past the date as long as they taste, look, and smell fine," Gunders says. Even the dates on pasteurized dairy products, such as milk, cheese, and yogurt, can be ignored because the pasteurization process kills harmful bacteria. Not even soured milk that's been in the fridge for months will give you food poisoning, Gunders says. Will it make you gag? Sure. But other than a nasty taste, it's fine.
If you have a question in your mind about whether a food is safe to eat or not, err on the side of caution and pitch it. Or cook it. Going the extra step of heating things will kill bacteria and make most products fine even after that increased risk, Gunders says. Salmonella, for instance, is destroyed after a food is cooked to 150 degrees or higher. Use your common sense, though. If something is green and slimy and completely unappetizing, you're better off tossing it. You won't get food poisoning, Gunders says, but it might not sit well in your stomach.