Today is the double feast of St. Antoninus. It is also Rogation Monday, a non-privileged greater feria. It is the first of the three days of the 'Lesser Litanies' sung on the days preceding the feast of the Ascension.
At Mattins, in the first nocturn, as there is no occurring Scripture for Rogation Monday the lessons are taken from the Common of Confessors, Fidelis sermo etc. The ninth lesson is of the commemorated Rogation Monday rather than SS Gordian and Epipmachus. At Lauds commemorations are sung of both the feria and SS Gordian and Epimachus.
The Little Hours of course have the Paschaltide Doxology sung at their hymns. The Domincal preces are omitted at Prime due to the occurring double feast.
Mass is sung after Terce. The Gloria is sung, a commemoration of the feria is sung, followed by a third collect of SS Gordian and Epimachus. The preface is that of Paschaltide and the last Gospel that of the feria.
Where the venerable practice of the Rogation Procession takes place the procession takes place after None. The antiphon Exsurge Domine is sung by the cantors and then the Litany of the Saints is sung: each invocation and its response being sung by the cantors and then repated by the choir. The celebrant wears a violet cope, the deacon and subdeacon violet dalmatic and tunicle respectively. When Sancta Maria, ora pro nobis has been sung all rise and the Cross-bearer leads the Procession accompanied by acolytes carrying candles followed by the cantors, choir and the ministers. The people follow. The Procession should, in theory, go around the parish with the Litany being repeated if necessary or the Penitential and Gradual Psalms added if the distance requires them. After the Procession re-enters the church the psalm Deus in adjutorium is sung and all kneel, the celebrant rises to sing the following ten collects. The Mass Exaudivit follows sung in ferial tones with violet vestments. The Gloria is not sung, the second collect Concede nos, the third Ecclesiae and Benedicamus Domino sung as the dismissal.
Where only one Mass is sung and there is the Procession the Mass Exaudivit is sung with commemorations of St. Antoninus and SS Gordian and Epimachus with Benedicamus Domino as the dismissal. Those with an obligation to the Office are bound to say the Litanies if they do not attend the Procession.
Vespers are of the feast without any commemorations.
In the 'liturgical books of 1962' St Antoninus is cut down to a third class feast of three lessons. Scriptural lessons have been inserted from the second chapter of St. Peter's Epistle. There is no third (or ninth obviously) lesson of the feria. The feria is not commemorated at Lauds or in Mass. SS Gordian and Epimachus are commemorated at Lauds and Low Mass. At the Little Hours the Paschaltide Doxology and its tone are not sung. Vespers are without any commemorations.
If the Procession takes place the Litany may be sung in the vernacular if the faithful are present. The petitions are not duplicated. In the votive Mass that follows all the 'preparatory prayers' i.e. In nomine Patris..., Introibo ad altare Dei..., Judica me Deus..., Confiteor Deo..., the versicles, Aufer a nobis... and Oramus te, Domine are all cut out. The dismissal is Ite, missa est.
The Bishop may transfer the Rogation Days to some other season as he sees fit (c.f. rubric pro loco 1962 Missale Romanum and c.f. Caeremoniale Episcoporum editio typica 1985 Cap. XIV, ## 381-384 for these directions in the completed, ordinary, form of the 1962 rite). The Bishop may also, following the 1962 books order prayers and/or supplications in place of the Litany where he sees fit to do so. Clergy must sing the Litanies in Latin but, as noted above, where the Procession takes place and the faithful are present singing the Litany in the vernacular is permitted. There is no longer any obligation to say the Litany in private if one does not take part in a Procession.