The chance of you catching lycanthropy is boosted on a full moon and zero on a new moon.

Werecreatures, including the player, never change into their beast form during new moon. (If a level is restored with the creature in beast form during new moon, it will be forced into normal form.)

The #attributes screen gives you several time-related pieces of info:

• The current time as observed by the game. (Possibly it should just tell you whether it’s night or midnight).
• How long it has been since you started the game in wallclock time, for speedrun checking.
• How long your current session has been.
• The current phase of the moon.

Moon phases affect the Plane of Water somehow.