No commemoration of St. Sylvester
Proper Mass (Dominica infra Octavam Nativitatis) found in the Missal immediately after the Nativity; Credo; preface and Communicantes of the Nativity, no commemoration.
Office of Dominica infra octavam Nativitatis, found in the Breviary immediately after the Nativity.
Matins: Invitatorium, Hymn, and 9 antiphons and 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); scriptural lessons 1 and 2 (=2 and 3) with their responsories from Dec. 31; lesson 3 proper to the Sunday within the Octave; Te Deum
Lauds: All is provided in the breviary for the Sunday within the Octave (the antiphons are the same as those of the Nativity), Sunday psalms.
Prime: Psalm 117 Confitemini is said (not Ps. 53 ut in festis); responsory verse Qui natus es
Hours: Sunday psalms and antiphons
I Vespers: Of the coming day, Octave of the Nativity, with no commemoration.
Compline: Of Sunday
Today, announce that tomorrow, January 1, is customarily observed as a Holy Day of Obligation in the USA.
The Te Deum is traditionally sung on December 31. It was enriched with a plenary indulgence under the usual conditions, as listed in the Raccolta, n. 684, 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.