Product best if used by yesterday

When San Francisco schoolchildren were nearly served cartons of three-month-old milk recently, a food handler told inspectors he was confused about what the expiration dates meant. That explanation hardly satisfied school officials or parents, but the worker had a point: Although the shelf life of milk should be pretty obvious, it's not always clear when other products have passed their prime. So U.S. News asked the experts about the life span of a few other items to see when expiration dates should be taken literally and when they can be stretched.