As most people will tell you, night is the time of the day in which a setting in fiction will generally be creepier, and the only time various monsters who are Weakened by the Light, such as Vampires and Werewolves, can be outside. So the solution to Horror movies, Survival Horror games and Big Boo's Haunt settings, where the undead are a necessary part of the setting and creepy, quiet atmosphere of night is needed constantly? Simple, it's Always Night, and if the sun ever rises, it'll appear just when all the danger is gone and the evil has been destroyed. See Grave Clouds for the variant where the weather is simply miserable at graveyards and other creepy areas, and which is possibly a sister trope to this. See also Evil Is Not Well Lit.