Monday and Tuesday of this week are both days within the Octave of the Epiphany and are of semi-double rite.
At Mattins the normal structure is followed, the special arrangement applying only to the feast itself. The antiphons and pslams are as on the feast (but the antiphons are not doubled) but in the third nocturn the psalm Fundamenta replaces the special arrangement of psalm 94. Lessons in the first nocturn are now, after the Sunday within the Octave, taken from St. Paul's letter to the Corinthians. Today the Incipit of the Corinthians is read, displaced from yesterday with the insertion of the Feast of the Holy Family on the Sunday within the Octave of the Epiphany. The first responsory, today, is Hodie but tomorrow will be Tria sunt. The second nocturn lessons today are from the writings of St. Fulgentius and tomorrow from St. Leo. In the third nocturn the homilies are from the writings of St. Ambrose today and from St. Chrysostom tomorrow.
At Lauds the antiphon on the Benedictus is proper for each day. Today a commemoration is sung of St. Hyginus. At the Hours the antiphons and psalmody is as on the feast, the hymns having the Doxology and melody of the Epiphany.
Mass today is of the resumed Sunday within the Octave, In excelso throno, the Gloria is sung, the second collect is of the Octave, the third is of St. Hyginus. The Creed is sung and the preface and communicantes are as on the Epiphany. Private Masses may be of the Octave with Gloria, second collect of the Sunday within the Octave, third collect of St. Hyginus, Creed, preface and communicantes of the feast. Vespers today are of the Octave with the antiphon on the Magnificat being proper to each day. Tomorrow Vespres will be first Vespers of the Octave Day of the Epiphany. Compline is festal.
In the 'liturgical books of 1962' the days after the Epiphany become IV class ferial days of Epiphanytide. Mattins has one nocturn and the psalmody is ferial. At the Hours the hymns do not have the Doxology in honour of the Epiphany and again have ferial psalmody. Mass today and tomorrow is of the former Sunday within the Octave Gloria is sung, the additional collects and Credo are omitted. St. Hyginus is commemorated at Low Masses today. Vespers has ferial psalmody as does Compline.