Trust Your Nose, Not the Sell-By Date
A sensible reminder from NPR's The Salt: Sell-by dates don't have very much to do with food safety, and the best way to tell if something's still edible is often just to look at it and give it a good sniff.
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There's no federal law when it comes to sell-by dates (with the exception of baby foods), so the date system is maintained without standardization by various food companies, which call a sell-by or use-by date when food may no longer be at its peak, rather than when it will be unsafe.
While dates can be a good guide for throwing out spoiled food, they're not as reliable as your senses. Depending on storage, perishable food will sometimes spoil a few days before the date on its label, sometimes a few days after. If your nose is in good working condition, it's far more accurate than a date stamp (especially when it comes to milk and meat).
Still, just because a food is safe, doesn't mean you'll want to eat it. In 1974, scientists found that home-canned corn, sealed circa 1934 in California "looked and smelled pretty much like ordinary canned corn." Canned food can last for many, many years, and tests showed that this corn hadn't degraded too much nutritionally. But no, scientists didn't care to taste the 40-year-old kernels. [NPR]