Saturday, September 8th
The Blessed Virgin Mary was born to St. Joachim and St. Anne, to be the famous WOMAN promised in the Proto-evangelium who would crush the head of the serpent.
This feast is a commemoration of that happy and joyful day on which the ever-blessed virgin Mother of God first saw the light of day. The Church accordingly sings on this day,
"Thy nativity, virgin Mother of God, has brought joy to the whole world; for from thee has come forth the Sun of justice, Christ the Lord, Who putting away cursing bestowed blessing, and by overcoming death obtained for us life eternal."
In the Introit of the Mass the Church sings:
"Hail, holy parent, who as a happy mother brought forth the King Who rules heaven and earth from eternity to eternity. My heart hath uttered a good word; I speak my works to the King."
The earliest document commemorating this feast comes from the sixth century. St.Romanus, the great ecclesiastical lyrist of the Greek Church, composed for it a hymn which is a poetical sketch of the apocryphal Gospel of St. James. St.Romanus was a native of Emesa in Syria, deacon of Berytus and later on at the Blachernae church in Constantinople, and composed his hymns between 536-556.
The feast may have originated somewhere in Syria or Palestine in the beginning of the sixth century, when after the Council of Ephesus, under the influence of the "Apocrypha", the cult of the Mother of God was greatly intensified, especially in Syria. St. Andrew of Crete in the beginning of the eight century preached several sermons on this feast.
Evidence is wanting to show why the eighth of September was chosen for its date. The Church of Rome adopted it in the seventh century from the East; it is found in the Gelasian (seventh cent.) and the Gregorian (eighth to ninth cent.) Sacramentaries. Sergius I (687-701) prescribed a litany and procession for this feast.
The church of Angers in France claims that St. Maurilius instituted this feast at Angers in consequence of a revelation about 430. On the night of 8 Sept., a man heard the angels singing in heaven, and on asking the reason, they told him they were rejoicing because the Virgin was born on that night; but this tradition is not substantiated by historical proofs.
The feast is found in the calendar of Sonnatius, Bishop of Reims, 614-31. Still it cannot be said to have been generally celebrated in the eighth and ninth centuries. St. Fulbert, Bishop of Chartres (d. 1028), speaks of it as of recent institution; the three sermons he wrote are the oldest genuine Latin sermons for this festival. The octave was instituted by Innocent IV (a. 1243) in accordance with a vow made by the cardinals in the conclave of the autumn of 1241, when they were kept prisoners by Frederick II for three months.
The Catholic Encyclopedia