Today is the feast of St. John the Apostle and Evangelist, it is a double of the second class with a simple octave.
The Office is again proper. As for all days until Epiphany hymns of Iambic metre have the special Doxology and tone in honour of the Incarnation. Mattins has three nocturns and the Nativity of the LORD is commemorated at Lauds, Mass and Vespers.
At Mass the Gloria and Credo are sung. The preface and communicantes are of the Nativity.
Vespers are of the Nativity but from the chapter of St. John. A commemoration of tomorrow's feast of the Holy Innocents is made and of the Octave of the Nativity.
In pre-1911 practice the day within the octave of St. Stephen's feast was also commemorated at Lauds, Mass and Vespers.
Following the 'liturgical books of 1962' the Doxology in honour of the Incarnation is omitted in the hymns of the Little Hours. At the Little Hours ferial antiphons and psalms are used. Vespers is of the Sunday within the Octave of the Nativity. No commemoration of the Octave is made nor is there any commemoration of the Holy Innocents.