The feast of all the saints began in the East as a practical necessity. Diocletian’s persecution in the late 3rd and early 4th centuries killed so many Christians that there weren’t enough days in the year to honor them individually, so the Church appointed one common day. Ephrem the Syrian attests to it at Edessa in 359 A.D. on May 13th. Chrysostom preaches it in Antioch on the Sunday after Pentecost around 407 A.D. The West had its own version of the same feast on that same Pentecost Sunday, preached by Maximus of Turin in the 5th century, and Rome’s earliest epistle list, the Comes of Wurzburg, still calls it the Sunday of the Nativity of the Saints using readings from the late 6th or early 7th century. In 609 A.D., Boniface IV received the Pantheon from Emperor Phocas, translated 28 cartloads of martyrs’ relics from the catacombs beneath its altar, and rededicated it as Santa Maria ad Martyres, fixing the Western commemoration on May 13th. Gregory III moved it to November 1st around 732 A.D. when he consecrated an oratory in St. Peter’s to all the Apostles, Martyrs, Confessors, and the Just resting throughout the world. Gregory IV extended November 1st to the entire Church around 835 A.D. at the request of Louis the Pious. The vigil on October 31st followed the feast as a matter of course. Then around 998 A.D., Odilo of Cluny added November 2nd as a day of prayer for all the faithful departed, completing what the tradition calls Hallowtide: All Hallows’ Eve, All Saints, and All Souls, a triduum centered on the dead in Christ, the known and the unknown.