Halloween is related to an ancient Celtic festival that took place in the fall, to celebrate the harvest. It is a time when days become shorter and colder,and darkness sets in earlier in the evening. All of this announces winter, and is therefore associated to death. The Celts believed that on October 31 the veil between the world of the living and the world of the dead became thin, and that the spirits of the dead could visit the earth; they called this festival, which took place on the eve of the Celtic new year, Samhain.