Saint Odilo (1049)

He was a saintly Benedictine and a great apostle of the souls in purgatory. Saint Odilo was the first to celebrate a special feast for All Souls (the souls of the faithful departed). This was in the year 998. The day Saint Odilo chose for this feast was November 2, the day after the feast of All Saints. All priests now have the privilege of saying three Masses for the souls in purgatory on November 2.

Saint Mayeul and Saint Odilo, abbots of Cluny, photo by Mangouste35Own work, CC BY-SA 3.0, Link