Night is irregular. What is not done in the daytime becomes possible at night: murder and sex and thought. Simple men are driven to early beds by tomorrow's daytime demands and by fear of the dark, and never dream of the irregular world outside. And all the while, a viscount and a spaceport baggage boy might be passing the night rolling bok ball in the city park. That's more than unusual -- that is irregular.
Alexei Panshin, The Thurb Revolution
irregular, night