Halloween, Hallowe'en or All Hallows Eve is celebrated on October 31st and is the Eve of the Christian celebration All Saint's Day or All Hallow's Day.
Halloween is the first day in the celebration of AllHallowTide, a 3-day celebration for honoring the dead. November 1st is Hallowmas, All Hallows Day or All Saint's day when Saints and martyrs are remembered. November 2nd is All Soul's Day, The Day of the Dead or The Commemoration of All the Faithful Departed, when one's own beloved dead are honored.
Many believe that Halloween and related Hallow Tide festivals evolved from various ancient Pagan festivals including Samhain(seems likely) and the Feast of Pomona(But we don't know much about that) and Parentalia, (but that's in February) or that they were created by the Church of Rome to replace the existing Pagan festivals as part of their conversion efforts.
Many people celebrate Halloween today as a secular holiday, celebrating with with activities that give a nod to its ancient roots related to death and spirits including costumed events such as trick-or-treating and parties parties, fortune telling, decorating the home with Jack-o-Lanterns and scary images, often relating to death, visiting haunted houses, mazes and forests, horror movie marathons and sharing scary stories.
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