Commemoration of St. Sylvester I, Pope and Martyr
Mass Puer natus assigned to the days within the Octave of the Nativity (in the Missal, immediately following December 28); Gloria; commemoration of St. Sylvester; Credo; preface and Communicantes of the Nativity
Matins: Invitatorium, Hymn, and 9 antiphons and 9 psalms from the Nativity (joined, not said as three nocturns); verse as found at the conclusion of the psalms for the Nativity (in its third nocturn); 3 lessons proper to December 31; Te Deum
Lauds: Antiphons of the Nativity with Sunday psalms; Hymn A solis ortus; commemoration of St. Sylvester
Hours: Ferial psalms and antiphons; remainder as on the feast of the Nativity
I Vespers: Of the Octave day of the Nativity: Proper antiphons, with psalms from the Common of the BVM; remainder proper
Compline: Of Sunday
The Te Deum is traditionally sung on December 31. It is enriched with a plenary indulgence under the usual conditions, as listed in the Raccolta (1950) n. 684 and in the Enchiridion (1999) n. 26, for those who attend the sung Te Deum on the last day of the year in order to give thanks to God for the blessings received from Him during the whole year.