Some equipment and monsters change behavior depending on the Time of Day.
|Daytime||06:00-18:00||Daylight Dagger, Arco De Velocidad, Fenrir items|
|Nighttime||18:00-06:00||Ninja Artifact Armor, Nightmare Sword, Fenrir items, Giant Bats spawn in outdoor areas, Diurnal mobs go to sleep|
|Dusk to dawn||17:00-07:00||Ninja Artifact Armor +1|
|Dusk||17:00-18:00||Lovers in the Dusk|
|?||20:00-04:00||Undead spawn in outdoor areas|
In-game dawn and dusk are different from their real-life counterparts in that the in-game ones are considered part of daytime rather than nighttime. (According to Wikipedia, dusk refers to a time shortly after sunset.)