In the Dark Ages and Early Middle Ages, the Catholic Church attempted to oppose the paganism involved in the Samhain festival by making November 1 All Saints’ Day and November 2 All Souls’ Day. As noted, All Saints’ Day was a remembrance and celebration of the saints, especially the ones who were heroic martyrs (people who died for their faith). All Souls’ Day became a day on which Roman Catholics prayed for the dead in order to help them escape the torments of purgatory.
In the year AD 609 or 610, Pope Boniface IV grievously strayed from biblical teaching by dedicating the Roman Pantheon, formerly a pagan temple to every known god, to the Virgin Mary and all Christian martyrs. This was done on May 13, a day that became a feast day. In 835 Pope Gregory IV transferred this feast to November 1 and extended it to include all of the saints. As a result, November 1, All Saints’ Day, the day after Halloween (Hallows’ Eve or All Saints’ Eve), became a day dedicated by the Catholic Church to the Virgin Mary and the saints. Eventually, November 2 evolved into All Souls’ Day, a special day to pray for the dead. As we will see, this custom supposedly originated with a mystical vision of the Catholic Saint Odilo, who died in 1048. - JOHN ANKERBERG