Today the Church celebrates the Nativity of the Blessed Virgin Mary. The Church has celebrated this feast since at least the sixth century. According to www.americancatholic.org, "A September birth was chosen because the Eastern Church begins its Church year with September. The September 8 date helped determine the date for the feast of the Immaculate Conception on December 8 (nine months earlier)." While the account of Mary's birth is not included in Sacred Scripture, the Protoevangelium of James, an apocryphal Gospel written around the year 150 A.D., provides some details.
There is much misunderstanding about Catholic belief in the role of Mary and our devotion to her. There are plenty of apologetic materials available which explain our beliefs in an understandable manner. The main point to remember is that we believe Mary always points us toward her Son, Jesus. The words she spoke at the Wedding Feast of Cana to the stewards applies well to all of us, "Do whatever he tells you." (John 2:5)