Michaelmas a day which, according to the Church of Rome, was set apart to express her thankfulness to God for the many benefits she had received by the ministry of holy angels; and called Michaelmas because St. Michael is alluded to in Scripture as an angel of great power and dignity, and as presiding and watching over the Church of God with particular vigilance and application, and as triumphant over the devil. It originated in some provincial festivities which were introduced between the 3d and 9th centuries, and which were then combined into one common celebration on the 29th of September, the day on which St. Michael's Church on Mount Garganus was dedicated, as mentioned in the Saxon Chronicle in 1011, and in Ethelred's laws in 1014. There is a tradition that this feast was instituted by Alexander, bishop of Alexandria. It was generally observed in the 8th century; in the 12th century by the Council of Mayence, and indeed by the whole Greek Church, in accordance with an injunction of the emperor Manuel Comnenus. The apparition of St. Michael, "the prince seraphim, leader of the angelic hosts, prefect of Paradise, and conductor of souls to the place of repose," to whom cemetery chapels and churches on hills were in consequence dedicated, was observed on the 8th of May. In the 10th century there was a curious superstition that on every Monday morning St. Michael held high mass in the churches.
The Greek and other Eastern churches, the Church of England, as well as several other evangelical churches, continue to observe the Feast of St. Michael, according to Wheatly, in order " that the people may know what benefits Christians receive by the ministry of angels" (On the Common Prayer, page 190).
The Romish Church, besides observing St. Michaelmas, also celebrates three appearances of St. Michael, which have happened (we are told) in these later years. The first is the appearance of this archangel at Colossus, in Phrygia; but at what time the Romanists do not know themselves. They observe September 6 as the day. The second is that of Mount Garganus, in the kingdom of Naples, about the end of the 5th century. May 8 is set apart as the day to commemorate the event. The third is his reputed appearance to Aubert, bishop of Avranches, upon a rock called the Tomb, where now stands the abbey of St. Michael. This was about 706. October 16 is observed in memory of this event. See Broughton, Biblioth. Hist. Sacra, 2:93; Procter, On the Book of Common Prayer, page 301; Wheatly, On the Common Prayer, page 253; Butler, Lives of Fathers, Martyrs, and Saints, 2:94; 3:177; Michaelis, Denkwiirdigkeiten a.d. christl. Archdol. 3:28 sq.