October 31 marks the observation of Halloween or Hallowe’en, a short variation of All-hallow-even, the evening before All Hallows Day or All Saints Day, on November 1. After the Romans conquered the Celts in 43AD, they adopted many of their festivals and incorporated them into their own religious celebrations. All Hallows Day was one such example. Originally the day that celebrated numerous pagan festivals, but Pope Gregory III would eventually designate November 1 to mark the Christian feast of All Saints Day, which had moved from May 13. According to the Church, a day started at sunset, which is why celebrations typically started on October 31, the eve of the holiday, All Hallows Day.