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.
The origins of Halloween can be traced back to the ancient Celtic holiday of Samhain, which fell on November 1 in modern calendars. People dressed up in costumes and lighted bonfires to scare off spirits on that day, as it was thought that the souls of the deceased returned to their houses.