Time

Quinn got a watch for Christmas, and has been wearing it alot lately.  He came into my room this morning and said ....
Quinn: "Mom, my watch isn't working!  It says it's 19:15 instead of 7:15!"
Mom:  "Oh, that's actually military time.  Since there's 24 hours a day, and only 12 hours on a clock, instead of saying 'a.m.' and 'p.m.' they just add twelve to whatever o'clock it is.  Get it?"
Quinn: "AAAAHHHHHH.  I get it.  It's a MATH WATCH."
Mom: "Uh, yeah.  Kinda."