December 11 is the anniversary of the founding of the Marian Fathers of the Immaculate Conception. On this day in 1670, St. Stanislaus Papczyński left the Piarist order and made his oblatio, his self-offering, to defend the Immaculate Conception.
The Christmas Octave concludes on Jan. 1, the beginning of a new calendar year and the Solemnity of Mary, Mother of God, a Holy Day of Obligation. Start the New Year off right!