Many consumers read an item's sell-by date as an indicator of when the food will spoil, which is an inaccurate assumption. Consumers are concerned about food-borne illnesses and freshness, becoming preoccupied with sourcing and safety.
Manufacturers use sell-by dates to help retailers manage their inventory. It encourages stores to sell a product within a specific time frame, so that the item still has a shelf life once it is purchased.
Expiration dates lead us to waste money and throw out perfectly good food.
Phrases like sell-by, use by, and best before are poorly regulated, misinterpreted and lead to a false confidence in food safety. They are simply producer estimates of how long the food will be at peak quality.
Researchers also blame an incoherent jumble of state and federal regulations and guidelines for unclear expiration date labels. The Food and Drug Administration leaves the determination of such dates up to manufacturers.
(Natural Resources Defense Council and Harvard Law School's Food Law and Policy Clinic, Use-by dates confuse shoppers, by Tiffany Hsu, Los Angeles Times, September 19, 2013)