Do you check the “sell by” dates of foods in the grocery store, avoiding anything that is past its “sell by” date? Do you toss food items out of the refrigerator once the “sell by” date is passed? If so, you’re not alone. For many, it’s a perceived issue of food safety. A commonly held belief is that those “sell by” dates are a legal requirement, determined by some federal government agency (the FDA?) to protect us from contaminated food.
In fact, food “sell by” and “best if used by” dates are not determined by the FDA, or by any other federal agency for that matter. They are simply estimates by the food's manufacturer of when the food passes some arbitrary measure of quality, such as taste, texture, or nutritiousness. After all, they don't want you buying their product and then not being happy with it. Retail stores are not required to remove food items from their shelves once the “sell by” date is passed. However, in order to maintain good customer relations many stores do discard them, or at least mark them down for quick sale. Some states require that certain food products have "sell by" dates, others don't.
The bottom line is that "sell by" dates are not designed to protect us from tainted food. That would be next to impossible, because because how a food product is stored and handled after it is produced (storage temperature, humidity, etc.) has a major role in how long it takes to spoil.
Granted, it’s hard to tell when a food actually has gone bad. Those “sell by” dates can certainly be an important clue. But in the final analysis, you the consumer are left to use your best judgment. Buy foods with the best “sell by” dates that you can, and be aware of how they have been stored in your home. If they’re supposed to be refrigerated, were they kept cold in transit? What’s the temperature in your refrigerator? Finally, use your senses. If it’s got mold on it and smells or tastes a bit off (or is way past it’s “best if used by” date) throw it away.
For an in-depth look at this subject, see "The Dating Game: How Confusing Food Date Labels Lead to Food Waste in America", a joint project of Harvard Food Law and Policy Clinic and the Natural Resources Defense Council.