Halloween is a festival that takes place in the u.s on October 31st. Halloween developed from ancient new year festivals and festivals of the dead. In the 800's A.C., the church established All Saints' Day on November 1st so that people could continue to celebrate a festival they had before becoming Christians. The Mass that was said on All Saints' Day was called Allhallowmas, which is how the evening before All Saints' Day became known as All Hallow e'en, or Halloween.
The Celtic festival of Samhain is believed to be the source of present-day Halloween celebration. The Celts lived well over 2,000 years ago and their new year began on November 1st. They usually celebrated a festival the previous evening which honored Samhain, the Celtic lord of death. It marked the beginning of a new season of cold,darkness and death.