The Requiem Mass didn't exist until not long before the end of the 10th Century, and a special day for the commemoration of the dead, November 2nd (All Soul's Day), was insitituted by St. Ode, the Abbot of Cluny, in 998. All Soul's Day was observed everywhere by the 13th Century when the doctrine of Purgatory, as taught by St. Thomas Aquinas (as well as several other theologians) was universally excepted and Masses for the dead became general feature in parish life. It would be correct to say that the Mass for the Dead, stemming from the Roman Missal promulgated by Pope St. Pius V in 1570, by decree of the Council of Trent, is of Franco-Gallican origin.