Discovering what everyone already knew

The act of coming across something that all of your friends already knew about. For example, the person who somehow made it through the last decade without knowing about that great taco joint that is a block away from the office could be said to have done this. Or the person who gets a Kuerig in 2018 and then tries to explain to everyone who's owned one for five years exactly how convenient they are. Or when your father-in-law finally gets a smartphone and then proceeds to tell you all of the advantages of smartphone ownership, as though you weren't aware.