IV class Requiem Masses are not permitted during the IV class ferial days of Christmastide and Epiphanytide.
Mass of the 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 from January 7-11 are from Romans, and those on January 12 are from I Corinthians. The proper Benedictus and Magnificat antiphons listed on those days are also used, in addition to the prayer Deus qui hodierna.
Matins: Invitatorium and Hymn from the Time of Epiphany; psalms and antiphons of the feria; scripture lessons of the calendar day (Romans); Te Deum
Lauds: Psalms and antiphons of the feria; capitulum and following from Time of Epiphany; Benedictus antiphon proper
Prime: Psalms and antiphons of the feria; 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 proper