Should November 2 fall on a Sunday, the commemoration of All Souls is transferred to the following Monday. Pope Benedict XV granted priests permission to offer three Masses on All Soul”s Day. One of these Masses the celebrant may say according to his own intention; one must be offered for all the faithful departed and the third for the intention of the Holy Father.
The Church with her usual sublime economy preserved all that was innocent, tender and inspired in the funeral rites of classic antiquity. She purified and spiritualized them, handing them on to the new generation of the Middle Ages transfigured by a new thought which gave a sense of joy and life to the Liturgy of the departed, the thought that they would rise once more like the risen Redeemer.
Therefore all that was dismal or frightening disappeared. There were no more emblems of death, skulls or cross-bones traced upon the draperies; all spoke instead of peace and serene hope.
The ancient Roman cemeteries, then, were not merely graveyards, they were country houses with baths and gardens adjoining them, where even the Popes themselves often resided.
The memento of the dead in the Mass is common to all Liturgies since the Third Century. In the Eighth Century we find among the customs of the monastery of Fulda that of celebrating each month a commemoration of the faithful departed with a special Office and special prayers. To pass from a monthly celebration to an annual one was easy, and thus we find that towards the Tenth Century, especially in Benedictine monasteries, the custom prevailed of commemorating every year the benefactors and friends of the house who had been taken from this world. St. Odilo, Abbot of Cluny, is generally recognized as having been responsible for the universal adoption of this custom, already in use in many churches. (998).
(Source: The New Roman Missal, Rev. F. X. Lasance)