Halloween or Hallowe'en, also known as Allhalloween, All Hallows' Eve, or All Saints' Eve, is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. Halloween originated with the ancient Celtic festival of Samhain and is now a. Halloween is the evening before the Christian holy days of All Hallows' Day (also known as All Saints' or Hallowmas) on 1 November and All Souls' Day on 2. Halloween, a holiday observed on October 31, the evening before All Saints' Day. All Hallows' Eve (October 31) and All Saints' Day (November 1) both paid homage to saints ("hallows" = saints). Halloween isn't just costumes and candy; it's a cultural holiday rich in tradition.