The Octave Before Christmas
December 17-23"The O Antiphons refer to the seven antiphons that are recited (or chanted) preceding the Magnificat during Vespers of the Liturgy of the Hours. They cover the special period of Advent preparation known as the Octave before Christmas, Dec. 17-23, with Dec. 24 being Christmas Eve and Vespers for that evening being for the Christmas Vigil."
December 20
"O Key of David,
opening the gates of God’s eternal Kingdom:
come and free the prisoners of darkness!"