In the Roman Catholic church, a day commemorating all the Christians believed to be in purgatory .
Celebrated on November 2, it was first established by Odilo (d. 1049), abbot of Cluny, in the 11th century, and it was widely celebrated by the 13th century. The date follows All Saints' Day , with the idea that remembering the saints in heaven should be followed by remembering the souls awaiting release from purgatory. Roman Catholic doctrine holds that the prayers of the faithful on earth will help cleanse these souls in order to prepare them for heaven.