Poe never reveals exactly what year "The Cask of Amontillado" takes place. Since the story was first published in 1846, it could have been at about the same time period. We do know that most of the story takes place at night--the time which Montresor knows will be the least likely for anyone to witness his act of revenge. Since it is the carnival season, Montresor has told his servants that he will be out, knowing that the servants will also leave the premises. The late night setting adds to the mystery and helps to build the suspense as Montresor leads Fortunato deeper into the catacombs. It also adds a certain creepiness and foreboding to this tale of murder.
According to the stroy "The cask of amontillado" take place at night and that was carnival time. the story is horor and short story friction so the night was best time to develop the story.