The observance of memorials is integrated into the celebration of the occurring weekday (the "feria") in accord with the norms set forth in the General Instructions of the Roman Missal and the Liturgy of the Hours.
The General Instruction of the Roman Missal lays down that, for memorials of saints, "unless proper readings are given, the readings assigned for the weekday are normally used. In certain cases, particularised readings are provided, that is to say, readings which highlight some particular aspect of the spiritual life or activity of the Saint. The use of such readings is not to be insisted upon, unless a pastoral reason truly suggests it." The Collect proper to the memorial is used or, if this is lacking, one from an appropriate Common. As to the Prayer over the Offerings and the Prayer after Communion, unless these are proper, they may be taken either from the Common or from the weekday of the current time of the year.
The General Instruction of the Liturgy of the Hours gives the following indications on celebration of memorials occurring on ordinary days: In the Office of Readings and at Lauds and Vespers:
- a) All the psalms with their antiphons are taken from the current weekday, unless the memorial has proper antiphons and psalms.
- b) If the memorial has its own antiphon for the invitatory, hymn, short reading, Benedictus and Magnificat antiphons and intercessions, these are used. Otherwise these elements are taken either from the Common or from the Office of the current week and day.
- c) The concluding prayer is taken from the Office of the saint.
- d) In the Office of Readings, the biblical reading with its responsory is that assigned to the weekday. The hagiographical second reading with its responsory is proper to the saint, but if no proper reading is assigned, the reading is either taken from the Common or is the patristic reading of the weekday
- e) Prayer during the Day and Compline are taken entirely from the weekday.
Celebrations of memorials occurring between 17 December and 24 December and during Lent, which are then never obligatory, consist of adding to the Office of Readings, after the patristic reading and responsory of the weekday, the hagiographical reading and responsory of the saint, and concluding with the prayer of the saint; and adding to Lauds and Vespers, after the concluding prayer of the weekday, the antiphon (proper or common) and the prayer of the saint.
Obligatory and optional memorials
Memorials are either obligatory or optional. The rules governing the celebration of memorials, whether obligatory or optional, are identical. The only difference is precisely that an optional memorial need not be observed, and, with the limitations indicated for the second part of Advent and for Lent, there is the possibility of celebrating instead the Mass either of another memorial assigned to that day, or of the weekday, or of any saint mentioned in the Roman Martyrology for that day, or indeed (except during the first part of Advent, the days from 2 January to the day before Epiphany, and Eastertide), a Mass for Various Needs, or a Votive Mass.
Sometimes even those memorials that are called obligatory cease to be such. This happens every year to those that happen to fall within Lent. If two obligatory memorials occur on the same day (as can happen when the movable memorial of the Immaculate Heart of Mary falls on the same date as a fixed obligatory memorial), both become optional.
The 1962 form of the Roman Rite
Celebration of the Roman Rite in its 1962 form, which remains authorised as an extraordinary form, follows the rules laid down in Pope John XXIII's 1960 Code of Rubrics. This did not use the term "memorial". Corresponding to obligatory memorials it had third-class feasts, as can be seen in the General Roman Calendar of 1962. In this calendar, some saints are, either permanently or because their celebration happens to coincide with a celebration of higher rank, given only a commemoration in the office actually celebrated.
In this form, the Office of a third-class feast uses the psalms of the weekday, unless proper psalms are assigned to the feast. In addition, the second and third readings for the ferial day at Matins are combined into the second reading, with a reading about the saint or feast providing the third reading. After the third reading the Te Deum is prayed. In Lauds and Vespers, everything after the psalms is either from the proper or the common of the feast. The same is done at Terce, Sext, and None. There are very few changes made at Prime. The office of Compline prayed for the feast is of the ferial day unless otherwise assigned.
Third-class feasts are merely commemorated on weekdays of Lent and are observed in no way on Sundays. During Advent, third-class feasts are observed together with a commemoration of the Advent ferial day, except during 17-23 December, days classified as second-class ferias, and thus of higher rank.
- General Norms for the Liturgical Year and the Calendar, 10
- General Norms for the Liturgical Year and the Calendar, 14
- GIRM, 357
- GIRM, 363
- GIRM, 355 a
- General Instruction of the Liturgy of the Hours, 235-236
- General Instruction of the Liturgy of the Hours, 239
- GIRM, 355 b-c
- Notification "Per Decretum die"
- The New Rubrics of the Roman Breviary and Missal. Surrey Hills, N.S.W.: The Catholic Press Newspaper Co. 1960.