But what is to be done in offices where a commemoration prayer and the prayer of the office is from the common? What must be done where the feast is the feast of a Doctor and a commemoration of a Doctor is to be made? What is to be done when the office of the feast is of a virgin not a martyr, and a commemoration of a virgin not a martyr is to be made? In the first case the prayer from the office of a confessor or Pontiff should be said, adding to it the title of Doctor. In the other case, the prayer Indulgentiam, omitting the word martyr, is to be said.
The origin of these commemorations was, that the Popes in removing the solemn celebrations of certain feasts of Apostles and Martyrs, which were formerly of precept, provided that their cultus should not be forgotten, and that their commemoration in the office should remind priests and the faithful of those servants of God, whom the Church wishes ever to honour. I have said the order given for commemoration in the Ordo should be followed; but not to follow this order does not exceed a venial sin. Even the deliberate omission of a commemoration in Lauds or Vespers is not a violation of a grave precept.
When several offices fall on the same day, only one office, the one of highest rank or most important, is said. The others are transferred or commemorated. The last section dealt with commemorations, and now we come to the difficult question of the translation of feasts. Title X. of the general rubrics must be read in connection with the Apostolic Constitution, Divino Afflatu (1911) and with the Abhinc duos Annos (1913).
Translation of a feast may mean the removal of a feast from an impeded day to a day which is free. Thus a feast of higher rank may fall on a feast day of a saint whose feast is of lower rank; the latter may then be transferred. Transference is either perpetual or accidental and temporary. The former applies to feasts which are always impeded by the meeting with a feast of higher rite on their fixed days. A feast which would fall on 6th January would suffer perpetual translation. This translation bears different names in rubrics, decrees and liturgical writings—translatio ad diem, fixam, translatio ad diem assignatam, mutatio, etc. Accidental translation means occasional transference, a transfer in one year and not in another.
Title II., section i, of the Divino Afflatu gives the characters of preferential rank which are to be considered in occurrence, concurrence or translation of feasts, Ritus altior, ratio primarii aut secundarii, Dignitas Personalis, solemnitas externa.