A happy little saying to help you avoid food poisoning. Let's say your milk is approximately 13 days past the expiration date. It hasn't become chunky, yet it does smell a little funny. You are in doubt as to whether or not you should drink it. Remembering this saying, you throw it out. Or, you could water your plants with it just to see if they die. The point is, you don't drink it. Vomiting is no fun.