"From early times liturgical honor was paid to all angels in the office of the dedication of the church of St. Michael the Archangel in Via Salaria on September 29... In Spain it became customary to honor the Guardian Angels not only of persons, but of cities and provinces... Outside of Spain, Francis of Estaint, Bishop of Rodex, obtained from Pope Leo X a bull in 1518 which approved a special office for an annual commemoration of the Guardian Angels in March. In England also there seems to have been much devotion to them... Pope Paul V authorized a special Mass and Office and at the request of Ferdinand II of Austria granted the feast to the whole empire. Pope Clement X extended it to the Western church at large as of obligation in 1670 and fixed it for the present date," October 2, "being the first free day after the feast of St. Michael."

Butler's Lives of the Saints, ed. Michael Walsh, Harper Collins, pp.312-313