A Cluniac Custom That Became the Whole West's

All Souls' Day falls on the second of November in the Western church, the day directly after All Saints, and the pairing is deliberate, one day for the saints already believed to be in heaven and the next for the ordinary faithful departed still, in Catholic theology, being purified before they arrive there. The observance is credited to Odilo, abbot of the monastery of Cluny, who instituted a commemoration of all the faithful departed for Cluniac houses around the year nine hundred ninety eight, to be kept on this date every year with prayers and Masses offered on behalf of souls in purgatory.

The custom spread outward from Cluny's network of dependent monasteries across the following two centuries until it was adopted generally across the Western church by the later Middle Ages, becoming one of the clearest liturgical expressions of the doctrine of purgatory as it had developed by that period. The Reformation is the hinge on which the feast's later history turns, since churches that rejected the doctrine of purgatory generally dropped the observance with it, so All Souls' Day remains distinctly a Catholic date today, kept by the Catholic Church and by some Anglican and Lutheran parishes with a high view of the practice, while most Protestant calendars carry no equivalent commemoration at all.