You go to the refrigerator for milk and notice that the date stamped on the bottle was yesterday. Do you drink it, or throw it away? Most people do the latter, which leads to far too much food being wasted, because those dates on the labels don't mean anything. That's according to research by my America Weekend guest, Emily Broad Leib, director of Harvard's Food Law and Policy Clinic. As she explained, there's no science behind expiration dates, and a big difference between "sell by" and "use by." Perhaps it's best to go back to the old smell-and-taste test before deciding whether to consume it or toss it.