If you’re interested in the inner workings and shifts in the history of the breviary and associated liturgical bits, you must not miss the series that the NLM is running. Today’s hits a major point: the changes to the breviary under Pius X—the first major modern liturgical meddling.  Here’s a bit in particular from the discussion of the kalendar:

In the Middle Ages, there was no idea of a General Calendar of Saints’ days to be observed universally. To be sure, there were many feasts which were observed universally, such as the principal feasts of Our Lady and the Apostles, the four great doctors of the Latin Church, and several of the more famous early martyrs and confessors. However, there was an enormous amount of local variation to calendars, which were regulated by local bishops and cathedral chapters with almost no direction from Rome. For this reason, one also finds some interesting gaps in medieval liturgical calendars, especially in regard to “new” Saints. The first Saint ever formerly canonized by the Apostolic See, Ulric of Augsburg, was never celebrated with a feast day in Rome itself. Pope Gregory IX, who reigned from 1227 to 1241, canonized both St. Francis of Assisi and St. Dominic. Despite the tremendous importance of these two religious founders to the life of the later medieval Church, neither appears in the 1556 edition of the Sarum Breviary, or the 1501 Breviary of Bamberg, (to give just two examples); in many other places, they were kept as mere commemorations. The same Pope once called the great preacher and miracle worker Saint Anthony of Padua “the Ark of the Covenant” while the Saint himself was still alive, yet his feast is missing from many late medieval calendars, and indeed, is not included in the 1568 Roman Breviary.

The Use of Rome had already been adopted by the Franciscans at time of their foundation, and was spread by them far beyond the confines of the Pope’s diocese. The new orders of the Counter-Reformation era such as the Jesuits and Oratorians also followed the Roman Use, and it soon became the standard liturgical form for all new religious orders and congregations. The Pian reform of the Roman Breviary was also taken on by innumerable dioceses throughout Europe and the newly-evangelized Americas, creating a liturgical uniformity much greater than had been known before Trent . The Catholic Church of the Tridentine era was particularly concerned, of course, to lay greater emphasis on the cult of the Saints, which had been so thoroughly rejected by the Protestant Reformers, and to add to the ranks of the heavenly intercessors its own great heroes. Therefore, when Saints like Ignatius of Loyola and Philip Neri were canonized, their feasts were more or less universally and immediately adopted, unlike those of their great medieval predecessors.

None of this will come as a surprise to medievalists but rather informs us on when and how the late and new uniformity occurred. It also explains what I have discovered—that the current Roman kalendar is simply unsuited for modern Anglicans however Rome leaning—the main current of unformity occurs after our departure thus quite a large percentage of saints in the kalendar are not part of the common heritage.