Григорий III
Pope Gregory III (731–741) dedicated an oratory in St. Peter's to the relics "of the holy apostles and of all saints, martyrs and confessors, of all the just made perfect who are at rest throughout the world". Some sources say Gregory III dedicated the oratory on 1 November, and this is why the date became All Saints' Day. Other sources say Gregory III held a synod to condemn iconoclasm on 1 November 731, but dedicated the All Saints oratory on Palm Sunday, 12 April 732.