[[Character A is standing behind Character B, who is sitting at a computer.]]
Character A: Hey, will you be in town the day after Christmas?
Character B: Couldn't say - I'm Jewish.
Character A: But.. how does being Jewish keep you from knowing your plans?
Character B: I know my plans - I just don't know when Christmas is.
Character A: Really? Why not look it up?
Character B:  Well, I'm also a physicist.
Character A: So?
Character B: I believe that since I don't observe Christmas, it can't have a definite date.
{{Title text: Physicists who want to protect traditional Christmas realize that the only way to keep from changing Christmas is not to observe it.}}