Today, November 21, we celebrate the Entry of the Theotokos into the Temple.
Today is the prelude of the good will of God, / of the preaching of the salvation of mankind. / The Virgin appears in the temple of God, / in anticipation proclaiming Christ to all. / Let us rejoice / and sing to her: / “Rejoice, O Fulfillment of the Creator’s dispensation.”
For a wonderful explanation of the connection between Mary, the feast of the Entrance of the Theotokos, and Christmas, please see the article Preparing for Christ’s Nativity: The Virgin Mary in Prophecy and Christian Tradition by Archbishop Dmitri of Dallas and the South (OCA).