According to an ancient text, not from the Bible, Mary was born to an aging couple, Joachim and Anna, who were considered barren. Joachim had been ridiculed for his lack of children and had left, but was told by an angel of God to return to his wife and unite with her. The birth of the Theotokos – the Greek term for God-bearer, the Mother of God – was therefore the result of normal conjugal relations, giving rise to Christ’s humanity and the redemption of the world. In the Catholic Church the Nativity of the Virgin Mary is a feast day, not a solemnity.
In the Orthodox tradition, the Church Year begins on September 1, which makes the Nativity of the Theotokos, celebrated on September 8, the first feast of the liturgical year. Correspondingly, the last festival of the liturgical year is the Dormition of the Theotokos on August 15. (Dormition is the passing of the Virgin Mary from earthly life.) The birth of the Virgin Mary is one of the 12 Great Feasts of the Orthodox Church.
For both Catholics and Lutherans, the liturgical year begins on the first Sunday of Advent.
