Christmas type holiday that can be thrown into any city/town.
The addition of “irrelevant” details adds local colour to a campaign world, giving the impression that the DM has thought very deeply about the history of even the smallest architectural feature.
Except, it doesn't have to be. Nighttime can be a relaxing, peaceful time in the world, when nature rests and soft shadows cover the ground. Not every night has to be filled with vampires, ghosts, beasts, and things jumping out from dark places.