The Churches of the East and the West celebrate liturgies in honor of Mary's birth from the sixth and seventh centuries on. The origin of the liturgy is traced to the consecration of the church in Jerusalem on the spot known as the shepherd's field and thought to have been the home of Mary's parents. The basilica was named in honor of St. Ann.
By the seventh century the liturgy was also celebrated in Rome where it had been introduced by monks from the East. From there, it spread throughout the West, and by the thirteenth century the liturgy had developed to a solemnity with a major octave (eight days of commemoration prior to the liturgy) and a solemn vigil which prescribed a fastday.
The date, September 8, was chosen as the 8th day (an octave) after the former Byzantine New Year. Although Mary's birth was celebrated on various dates throughout the centuries, September 8 predominated. The feast celebrating Mary's Immaculate Conception, December 8, (a liturgy instituted later) was set to correspond to nine months before Mary's birth. Just as the Annunciation (March 25) is nine months from the Birth of Our Lord.
In the East, Mary's birthday is celebrated as one of the twelve great liturgies. The title for the liturgy in the East: "The Birth of Our Exalted Queen, the Birthgiver of God and Ever-Virgin Mary." The present feast forms a link between the New and the Old Testament. It shows that Truth succeeds symbols and figures and that the New Covenant replaces the Old. Hence, all creation sings with joy, exalts, and participates in the joy of this day. ... This is, in fact, the day on which the Creator of the world constructed His temple; today is the day on which, by a stupendous project, a creature becomes the preferred dwelling of the Creator.
The responsory for the liturgy proclaims: our birth, Birthgiver of God, announced joy to the whole world. From you came the Sun of Justice, Christ our God. He released the curse and gave the blessing.