In the modern period of the Breviary’s history, it is the Church herself who undertook the work of reformation, and one of the chief results of the holy Council of Trent was to have set on foot the movement towards the unification of the divine office. Notwithstanding all that was done to render further correction unnecessary, it was not long before it was felt and stated that this Breviary still left something to be desired, and the successors of St. Pius V. made no difficulty in yielding to the requests for improvement addressed to them. Perhaps Urban VIII. went too far in his corrections, but he was soon to be surpassed by others.
Without troubling themselves to obtain the consent of the supreme authority, local churches, and among them nearly all the dioceses of France, thought fit to try their hand at reforming the Breviary, to the detriment of the unity of the faith. The pontifical authority, while deploring these mistaken attempts, was nevertheless alive to the importance of questions relating to the reform of the Breviary, and sought for means whereby to satisfy all reasonable objections. Until the present time, nothing has ever gone beyond the stage of mere suggestions; the church, in the wise deliberation characteristic of her, has not thought fit to carry them out. She has rested satisfied with modifications in matters of detail, while at the same time continuing to enrich the calendar by adding fresh saints’ days. In order the better to follow the stages in this period of the Breviary's history, we shall divide it into three chapters:—(1) The Council of Trent and the Breviary of St. Pius V.; (2) The Roman Breviary from St. Pius V. to the end of the eighteenth century; (3) The Roman Breviary in the nineteenth century. In an appendix will be given a bird’s-eye view of the changes which the Roman calendar has undergone in the past.