purple o'clock

The time of night when everyone in a group has become so giddy and sleep deprived that everything becomes funny.

Everyone: *giggling over nothing*
Person A: Oh man, is it purple o'clock already?

Person B: Probably, let me check.

Person B turns to Person C and looks them in the eyes.

Person B (with a straight face): Purple.

Person C: *begins laughing hysterically*
Person B: *also begins to laugh* It's definitely purple o'clock.