According to the BBC , Odilo, Abbot of Cluny first designated All Souls’ Day in the year 998. While Christians had always prayed for the dead , this time, there was a specific day dedicated to remembrance and prayer. The fact that it falls so close to Halloween is no accident: according to History.com, it’s widely believed that church officials chose the dates for both All Saints’ Day and All Souls’ Day in an attempt to replace Samhain , a Celtic festival that took place on November 1. The evening before All Saints’ Day became All Hallow’s Eve, or Halloween.