What Food Expiration Dates Really Mean

What does the "sell by" date on the milk carton actually mean? Is the yogurt still good a day after its "best by" date? Why does the canned soup say "best by 2028," and why doesn't the butter have a date at all? And how did the eggs get a date that's already passed when you only bought them last week?

There ought to be a law. But there isn't, at least not for most food. Here's the surprising truth: with one exception, the dates on food packages aren't about safety at all. They're about quality, and they're chosen by the company that made the food.

Here's what each date really means, which ones to take seriously, and how to stop throwing out perfectly good food.

The Big Surprise: Most Dates Aren't Federal Rules

The only food that federal law requires to carry a date is infant formula. For everything else, dates are voluntary. Manufacturers decide whether to print one, which words to use and how long to give the product. A few states have their own rules for milk and eggs, but there's no national standard.

That's why dates are so confusing, and why so much good food ends up in the trash. The USDA estimates that 30 to 40 percent of the U.S. food supply is wasted, and confusion over date labels is a big part of it.

Best By vs. Use By vs. Sell By

This is a quality date. It tells you when the food will taste its best: the crackers at their crispiest, the cereal at its crunchiest. After that date, the food may be a little stale or less flavorful, but it isn't unsafe if it's been stored properly. This is the date you'll see on most shelf-stable food, like cereal, crackers, canned goods and condiments.

"Use By"

This is the last date the manufacturer recommends for peak quality. On shelf-stable food, it's still about quality. But on highly perishable food, like deli meat, fresh fish, bagged salad and ready-to-eat refrigerated food, take it seriously. Use it by that date, or freeze it before then.

"Sell By"

"Freeze By"

Freeze the food by this date to keep its best quality. Once it's frozen, the date doesn't matter anymore. Food kept at 0°F stays safe indefinitely.

"Expiration Date" or "Exp."

You'll see this most on infant formula, baby food, vitamins and some medications. On infant formula, it's a firm deadline. On other food, treat it like a "use by" date.

The Dates You Should Never Ignore

• Infant formula: Never use it past the "use by" date. After that date, the nutrients may break down, and the formula may not flow through the nipple properly.
• "Use by" on perishables: Deli meat, smoked fish, refrigerated ready-to-eat salads and similar foods. Listeria, a dangerous bacteria for pregnant women, older adults and anyone with a weakened immune system, can grow slowly even in the fridge.
• Anything you've opened: Package dates apply to unopened food. Once you open it, the clock starts over. A jar of pasta sauce dated next year is good for about 5 days once it's open.

How Long Is Food Good After the Date?

It depends on the food and how you've stored it, not on the date. Here's a quick guide for unopened food that's been stored properly:

For storage times for nearly everything in your kitchen, see my food shelf life guide.

How to Read the Date on Eggs

Egg cartons can carry two dates. The "sell by" or "exp" date is for the store. Eggs are still good for 3 to 5 weeks after you buy them, even if that date passes in the meantime.

Cartons with the USDA grade shield also have a three-digit pack date, usually printed near the plant code on the end of the carton.

It's the day of the year the eggs were washed and packed: 001 is January 1, 365 is December 31. So a carton marked 310 was packed on November 6. Look for the highest number in the case, and you'll get the freshest eggs.

What About Codes on Canned and Boxed Food?

Many shelf-stable products, like canned soup, tuna and cake mix, have a string of letters and numbers stamped on the lid or bottom. That's a pack code. It's for the manufacturer (not you) to track when and where the food was made, in case of a recall. (There's a scary thought.) Some include a readable date; many don't.

If you can't read the code, write the month and year you bought the can on the lid with a marker and follow the times in the chart above. And whatever the date says, toss any can that's bulging, leaking, rusted or deeply dented, especially along the seam.

How to Stop Throwing Out Good Food

• Shop the back of the case for milk, yogurt and meat. Stores put the oldest dates up front.
• Rotate at home. Put new groceries behind the old ones in the fridge and pantry, so the oldest gets eaten first.
• Freeze before the date. Bread, meat and leftovers freeze beautifully. Here's how to freeze food the right way.
• Keep your fridge at 40°F or below. A warm fridge spoils food long before the date. Here's how to store food in the fridge.
• Use your senses for quality, not safety. Stale crackers and slightly soft carrots are fine. But the bacteria that cause food poisoning usually don't change how food looks or smells, so don't sniff-test raw meat or leftovers past their time. When in doubt, throw it out.

Food Expiration Dates: Quick Answers

What's the difference between best by and use by?

"Best by" is about quality: when the food tastes best. "Use by" is the last day the manufacturer recommends for peak quality. On perishables like deli meat and fresh fish, follow the use-by date closely.

Is it safe to eat food after the best by date?

Usually, yes, if it's been stored properly and shows no signs of spoilage. "Best by" dates are about flavor and texture, not safety. The exception is infant formula.

What does sell by mean?

It tells the store how long to display the product. It's not a safety date. Most food is still good for days or weeks after its sell-by date if you store it properly.

How long are eggs good after the sell by date?

Eggs are good for 3 to 5 weeks from the day you buy them, even if the sell-by date passes during that time. Keep them in the carton on a fridge shelf, not in the door.

Which foods are required to have expiration dates?

Only infant formula, under federal law. A few states require dates on milk or eggs. All other food dates are voluntary.

Keep Going

Keep your food fresh and your family healthy with these related guides:

• Food Shelf Life Guide: How long food really lasts in the fridge, freezer and pantry.
• Food Safety at Home: Safe cooking temperatures, thawing and leftovers.
• How to Store Food in the Fridge: What goes on every shelf, and why.
• How to Freeze Food: Stop freezer burn and thaw it safely.
• Kitchen Food Storage Tips: Organize the pantry so you can see what you have.
• The Pre-Thanksgiving Fridge Purge: Make room for the turkey.
• Fridge Odor Removal Tips: For when something in there has gone very wrong.
• How to Clean a Kitchen: Seven steps and the germiest spots.