IV class Requiem Masses are not permitted during the IV class ferial days of Christmastide and Epiphanytide.
Mass of the 1st Sunday after Epiphany; Gloria; no Credo; preface of the Epiphany without proper Communicantes.
Nota bene: The principal parts of the office during these seasonal ferias (until January 12) are from January 6, but are all listed together for convenience in the Ordinarium, under Time of Epiphany. The scripture lessons are from I Corinthians, listed in the breviary after January 13 as infra hebdomadam I post Epiphaniam. The scripture lessons listed before January 13 and assigned to January 7-12 (from Romans) are omitted. However, the proper Benedictus and Magnificat antiphons listed on those days are used, in addition to the prayer Vota quaesumus which is used for the days Post dominicam I post Epiphaniam, instead the prayer Deus qui hodierna.
Matins: Invitatorium and Hymn from the Time of Epiphany; psalms and antiphons of the feria; scripture lessons of Tuesday in the week after the I Sunday after Epiphany; Te Deum
Lauds: Psalms and antiphons of the feria; Hymn O sola magnarum; Benedictus Vidimus
Prime: Verse Qui apparuisti
Hours: Psalms and antiphons of the feria; capitulum and following from Time of Epiphany
Vespers: Psalms and antiphons of the feria; capitulum and following from Time of Epiphany; Magnificat Interrogabat