Anyone who can do basic math knows that something mysterious happened to a young Jewish girl named Mary nine months before Christmas.

On the early Christian calendar, March 25 was designated as the Feast of the Annunciation -- one of Christianity's great holy days. This feast centers on the passage in the Gospel of Luke in which the Archangel Gabriel appears to the Virgin Mary, announcing that she will conceive and bear a son.

"You have to think this through," said the Rev. Rudy Gray, a veteran Southern Baptist pastor in South Carolina who now leads the state's Baptist Courier newspaper. "If there is no conception, there is no virgin birth of Jesus. Without that you have no sinless life that leads to the crucifixion. Without the cross you don't have the resurrection and the resurrection is the heart of the Christian faith."

In St. Luke's Gospel, Mary responds with a poetic song that begins: "My soul doth magnify the Lord, and my spirit hath rejoiced in God my Savior. For he hath regarded the low estate of his handmaiden: for, behold, from henceforth all generations shall call me blessed."

The Latin translation became known as "The Magnificat," a text familiar to all Catholics who follow the church's holidays. The Annunciation is a major feast in Eastern Orthodoxy and this holy day is observed, to some degree, in other Christian bodies that use the ancient church calendar.

However, in many churches this holy day has vanished. The bottom line is that many Protestants are clear when it comes to knowing what they don't believe about Mary, but not at all sure about what they do believe about this crucial biblical character.