The Question asked in a combox was:
Fr Gregory, I am a new user to the Anglican Breviary and I’m slightly confused by the number of Sundays after Pentecost or Trinity from the Breviary. On the previous Sunday, I tried to use the Magnificat Antiphon as reference point and compared between the Latin Breviary on the internet with AB. I found out that on XXI Sunday after Pentecost, all the Propers should be from XXII after Trinity in the AB. But I always thought the counting of Sundays after Trinity should be one number behind that of Sundays after Pentecost. Could you give me some help here?
The answer follows:
In the Anglican Breviary (AB) the 1st Sunday after Trinity is the Sunday within the Octave of Corpus Christi but the AB reads the Gospel for Book of Common Prayer’s Trinity I (Lk. 16). In the Roman Breviary (1962) the 1st Sunday after Trinity is counted as the 2nd Sunday after Pentecost and it (obviously) reads the Gospel for the 2nd Sunday after Pentecost (Lk 14). The AB reads for the 2nd Sunday after Trinity the Gospel assigned (obviously) for Trinity II (Lk 14) which corresponds to the Gospel read for Pentecost II in the RB.
RB Pentecost II = Lk. 14 while the AB counts Trinity I (Oct. of Corpus Christi) = Lk. 16.
RB Pentecost III = Lk. 15 and the AB Trinity II = Lk. 14
RB Pentecost IV = Lk. 5 and the AB Trinity III = Lk. 15
But then something happens here which changes the relation between Pentecost and Trinity:
RB Pentecost V = Matt. 5 and the AB Trinity IV = Lk. 6
RB Pentecost VI = Mark 8 and the AB Trinity V = Lk 5
RB Pentecost VII = Matt. 7 and AB Trinity VI = Matt. 5
RB Pentecost VIII = Lk. 16 and AB Trinity VII = Mark 8
So that RB Pentecost XXI corresponds to AB Trinity XXII.
The AB follows the lectionary of the Book of Common Prayer rather than the Tridentine version of the (1962) RB.