The Christmas Novena began on December 16
You can find out about the Christmas Novena here:
A Christmas novena is usually prayed, starting nine days before Christmas. The following novena was composed by an Italian priest, Rev. Charles Vachetta, C.M., in 1721. Most of the material comes from the Old Testament prophecies and the Psalms referring to the promised Redeemer.The novena consists of Opening Responsory Prayers, Psalm (Let the Heavens Be Glad), Scripture Reading, Magnificat with Daily Antiphon and Closing Prayer.This novena is prayed in conjunction with the O Antiphons, and if you are using an O Antiphon House or Tower, you would open the windows during this prayer.
And more about novenas in general in this book:
