All Souls' Day, Nov. 2 (exceptionally, Nov. 3), feast of the Roman Catholic Church on which the church on earth prays for the souls of the faithful departed still suffering in purgatory. The proper office is of the dead, and the Mass is a requiem. General intercessions for the dead (e.g., for those of a parish, a city, or a regiment) are very ancient (2 Mac. 12.43–45); but the modern feast was probably first established by Abbot Odilo of Cluny (d. 1049) for his community and later extended throughout the church. In Catholic countries there are many customs peculiar to All Souls' Day (e.g., leaving lights in the cemeteries on the night before). These vary from region to region. They should be distinguished from the customs of Halloween, which were apparently an independent development (see All Saints' Day).