Halloween originated from the ancient Celtic festival of Samhain, which was celebrated at the end of the harvest season and believed to be a time when the souls of the dead could commune with the living. As Christian missionaries converted the Celtic people, they attempted to replace their pagan rituals with a Christian-focused All Saints' Day, though many of the older traditions remained. Today, Halloween is a holiday associated with costumes, trick-or-treating, jack-o-lanterns, and superstitions about divination and contacting spirits of the dead.