Today is the Octave Day of the Epiphany, it is of greater-double rite.
At Mattins in invitatory and hymn are sung as on other days within the Octave, the special arrangment being for the feast only. The antiphons and psalms sung are those used on the feast. In the first nocturn the lessons are from the Epistle to the Corinthians, Audet aliquis (for Wednesday after the first Sunday after the Epiphany). The first responsory sung today is Hodie [pun intended!]. In the second nocturn the lessons are from a sermon of St. Gregory the Theologian and in the third nocturn the homily if from St. Augustine.
At Lauds all is as on the feast, including the antiphon on the Benedictus, but the collect is proper to the Octave Day Deus, cujus Unigenitus.
At the Hours the hymns have the Doxology and melody of the Epiphany. The antiphons and pslams are as on the feast with the collect of the Octave Day.
Mass is sung after Terce. The Mass formulary is the same as on the feast except the orations and Gospel are proper. The Gloria is sung, the Creed is sung and the preface and communicantes are of the Epiphany.
Vespers are of the Octave Day with commemorations of tomorrow's feast of St. Hilary of Poitiers and St. Felix.
In the 'liturgical books of 1962' the Octave, and of course the Octave Day, have been abolished. The former Octave Day was 'resprayed' as the feast of the Baptism of the LORD in the 1955 assault on the Liturgy and celebrated as a greater-double. In the 1960/61 revisions the feast became II Class. Mattins and Lauds are as in the Old Rite. At the Hours the ferial psalter with its antiphons is used. The hymns do not have the Doxology in honour of the Epiphany. At Mass the special communicantes used throughout the Octave in the Usus antiquor are not said.