Every year on September 8, the Church joyfully celebrates the Nativity of the Blessed Virgin Mary, honoring the birth of the woman chosen to become the Mother of God. It is a feast filled with hope and gratitude, but it also raises a common question: How do we know that Mary was born on September 8?

The simple answer is that we do not know her actual birth date. Sacred Scripture does not record when Mary was born, nor does it provide details about her early life. Instead, the Church celebrates her birth through a long-standing Christian tradition that highlights her unique role in God’s plan of salvation.

The origins of this feast can be traced back to fifth-century Jerusalem. Near the Pool of Bethesda, Christians built a basilica on a site traditionally believed to be the birthplace of the Blessed Virgin Mary. Every year on September 8, the faithful gathered to commemorate the dedication of that church, and over time, the celebration naturally became associated with Mary’s birth.

As devotion to the Blessed Virgin spread, so did the feast. What began as a local celebration in the Holy Land was embraced throughout the Eastern Church before eventually being adopted by the Western Church. Today, it remains one of the oldest and most cherished Marian feasts in the Church’s liturgical calendar.

The celebration of Mary’s birth is also closely connected to the Feast of the Immaculate Conception on December 8. The Church commemorates Mary’s conception without original sin on that day, and exactly nine months later, celebrates her birth on September 8. Although the Nativity of Mary was celebrated before the Immaculate Conception was formally established, the two feasts now beautifully complement one another in the liturgical year.

More than commemorating a date, this feast celebrates what Mary’s birth signifies. Her arrival into the world marks the beginning of God’s visible preparation for the coming of His Son, Jesus Christ. Before the Savior would be born in Bethlehem, God first prepared the one who would become His Mother.

The Church celebrates only three birthdays in its liturgical calendar: the birth of Jesus Christ on December 25, the birth of St. John the Baptist on June 24, and the birth of the Blessed Virgin Mary on September 8. Each birth marks a decisive moment in salvation history and reveals God’s unfolding plan to redeem humanity. Mary’s birth, in particular, is celebrated because she was chosen to cooperate freely with God’s saving work.

The Fathers of the Church often described Mary’s birth as the dawn before sunrise. Just as the first light of morning announces the coming of the sun, Mary’s birth announces the coming of Christ, the Sun of Justice. Her life points not to herself but always to her Son, who is the light of the world.

Reflecting on this mystery, St. Andrew of Crete beautifully proclaimed: “Today the Creator of all things has prepared a dwelling place for Himself. Today humanity, in all the radiance of her spotless nobility, receives its ancient beauty.” His words remind us that Mary’s birth marked the beginning of a new chapter in God’s saving plan, one that would culminate in the Incarnation of Jesus Christ.

For Catholics, therefore, September 8 is not about identifying Mary’s historical birthday with certainty. Rather, it is a joyful liturgical celebration that gives thanks for the beginning of the life of the one through whom God prepared the coming of our Savior. As we honor Mary’s birth, we celebrate God’s faithfulness, His perfect plan, and the hope that entered the world through the Mother of Christ.