The Annunciation celebrates the angel Gabriel's announcement to the Virgin Mary that she would conceive and bear the Son of God (Luke 1:26-38) — the moment when, in the words of the Nicene Creed, the Son of God 'was incarnate by the Holy Spirit of the Virgin Mary.' It is simultaneously a Christological feast (celebrating the Incarnation) and a Marian feast (celebrating Mary's faithful 'yes' — her fiat). Observed on March 25, exactly nine months before Christmas, the feast is the theological hinge of the Christian year: the Incarnation that makes the Nativity, Passion, and Resurrection possible.