Random odd thing

I just noticed that the plastic lid of my convenience-store coffee cup has "12/16/20" written on it. What's that supposed to be? The expiration date? (I really love that there's an expiration date on bottles of distilled water. As far as I know, nothing can ever happen to distilled water in a sealed container. You could probably drink it a hundred years from now. But maybe the expiration date is for the plastic.)