有效期就是让你把没用掉的扔了再买新的

我以前在宾州见到过专卖到了有效期的食品店，便宜的一塌糊涂。

网上查了一下

It is illegal for stores to sell food past its “Use By” date. However, stores are allowed to sell food after it has passed the “Best Until” “Best Before” “Sell By” or “Display Until” dates stamped on the sides of packages.