IV. Concerning the Occurrence and Translation of Feasts and Their Concurrence

1. Feasts of Doubles of the first and second class, both of the universal Church and proper to some place, impeded even perpetually, any privilege up to now granted to certain Feasts being removed, are to be transferred to the first following day not impeded by any Sunday or by the Vigil of Epiphany, by another Feast of Double of the first or second class, or by Offices excluding Feasts of this kind respectively. The same Feasts, both of the first and of the second class, in second Vespers do not admit a Commemoration of the following day within an Octave, nor of any Simple Office, even if on the next day the whole Office is to be celebrated of them.

2. But greater or lesser Double Feasts or Semidouble Feasts which are celebrated in the universal Church, if they have been accidentally or perpetually impeded, are not transferred, but a Commemoration is made of them according to the Rubrics, and the ninth historical Lesson is read. If nevertheless the impeding Feast was a Double of the first class of the Lord of the universal Church, nothing is made of the Feast impeded as above; but if it was another Double of the first class, of the impeded Office only a Commemoration is made at Lauds and in private Masses, and the ninth Lesson is not read.

The same is observed concerning Feasts proper to some Nation, Diocese, Order, or Institute, which likewise, if in some particular Church they have been impeded on their own day, are commemorated or omitted, as above. But proper Feasts of some Nation, Diocese, Order, Institute, or particular Church, which in the whole Nation, Diocese, Order, Institute, or in their particular Church are impeded, if the impediment is accidental, are likewise commemorated or omitted as above; if the impediment is perpetual, they are replaced on the nearest day not impeded by a Double Office, by a Semidouble Feast, by privileged Vigils, and by Octaves of the second order.

But concerning Feasts of this kind, greater or lesser Doubles or Semidoubles, which are impeded perpetually or even accidentally, private Masses can be said at the will of the priest, provided the impeding Office was not a Double of the first or second class, any Sunday, an Octave of the first or second Order, an Octave Day of the third order, a privileged Feria or Vigil. This Mass is said with festive rite, with the second Prayer of the Office of the day and others from Commemorations perhaps occurring. (1)

Feasts which up to now both in the universal Church and in particular places have been celebrated under semidouble rite ad libitum are to be reduced to simple rite, and concerning them a Commemoration is to be made whenever they are impeded, as is done concerning other Simples according to the Rubrics. Nevertheless the Feast of St. Canute yields to the Feast of Saints Marius, etc., Martyrs, and therefore is commemorated in its Office.

4. If the secondary Patron of a place, or another proper Saint, has been described in the Calendar with other Saints, he is not to be separated from them; rather, of all together the Feast is celebrated under the rite of greater or lesser Double, or Semidouble, according to the Rubrics, unless it is described in the Calendar under a higher rite.

5. When some greater or lesser Double Feast, or Semidouble Feast, occurs on a greater non-privileged Double Octave Day of the same Person, the Office is made of the Feast, under the rite befitting the Octave Day, the Commemoration of the same Octave being omitted or added according to the Rubrics.

(1) Hence, for example, for the Society of Jesus, on February 5, Masses can be said ad libitum either of the Holy Martyrs of the Society of Jesus with commemoration of St. Agatha, or of St. Agatha with commemoration of the Holy Martyrs of the Society of Jesus.

Hence it also follows that if a Regular Priest celebrates in a foreign Church, he can at will say Mass either of the Saint whose feast is being kept in that Church, or of the simplified Saint in the Calendar of that same Church. Wherefore it is not lawful for one of the Society of Jesus celebrating in a foreign Church on February 5 to read ad libitum the Mass of St. Agatha or of the Holy Martyrs of the Society of Jesus, if either is not simplified in the Calendar of the said Church, but only of the Saint whose feast is being kept on the day.

Nevertheless the exception remains firm of the case in which someone about to celebrate in a foreign Church on the feast day of some Saint of semidouble or simple rite in the same Church can celebrate the Mass ad libitum either of the same semidouble or simple Saint, or of the Saint assigned in his own Calendar, and indeed with festive rite. Sacred Congregation of Rites, n. 3892, ad V.