J. Kenji López-Alt at the NYT:
Food product dating, as the U.S. Department of Agriculture calls it, is completely voluntary for all products (with the exception of baby food, more on that later). Not only that, but it has nothing to do with safety. It acts solely as the manufacturer’s best guess as to when its product will no longer be at peak quality, whatever that means. Food manufacturers also tend to be rather conservative with those dates, knowing that not all of us keep our pantries dark and open our refrigerators as minimally as necessary.