The Feast of St. Michael and All Angels

Luther Reed in The Lutheran Liturgy writes that the feast of St. Michael and All Angels commemorates the dedication, on a 29th of September sometime in the 5th century, of a small basilica on the Via Salaria, near Rome, the first church in Italy dedicated in honor of the Archangel Michael. In England Michaelmas is the traditional beginning of the Fall terms of courts and universities.

O everlasting God, who hast ordained and constituted the services of Angels and men in a wonderful order: Mercifully grant, that as thy holy Angels alway do thee service in heaven, so by thy appointment they may succor and defend us on earth; through Jesus Christ our Lord.

(The Book of Common Prayer [1662] of the Church of England)

Deus qui miro ordine angelorum ministeria hominumque dispensas: concede propitius vt a quibus tibi ministrantibus in caelo semper assistitur: ab his in terra vita nostra muniatur. Per dominum.
                Gregorian