Today, September 8th, we celebrate the Nativity of the Blessed Virgin Mary. My kids and I went to Mass and baked cupcakes.
Go to New Advent for details on the history of this feast.
Basically, the feast was celebrated at least by the 6th century. Our written source for details on Mary's nativity come from a document written in 150 A.D. called the Protoevangelium of James. It tells us that Mary's parents are named Joachim and Anne. They had no children until an angel appeared to Anne and told her she would conceive.
September 8th, it should be noted, falls exactly 9 months after the feast of the Immaculate Conception of Mary.
Mary's birthday is important to salvation history because she is the Mother of God. The Lord asked her to carry His son in her womb and raise Him. Her obedient yes -"Behold the handmaid of the Lord; be it done to me according to your word" (Luke1:38) brought Jesus to us. She is always bringing her son to us. "Do whatever he tells you" (John 2:5) she says to the servants, but also to us.