The Tridentine calendar is the calendar of saints to be honoured in the course of the liturgical year in the official liturgy of the Roman Rite as reformed by Pope Pius V and first issued in 1568, implementing a decision of the Council of Trent, which entrusted the task to the Pope.
The Apostolic Constitution Quod a nobis, which imposed use of the Tridentine Roman Breviary, and the corresponding Apostolic Constitution Quo primum concerning the Tridentine Roman Missal both decreed: "No one whosoever is permitted to alter this letter or heedlessly to venture to go contrary to this notice of Our permission, statute, ordinance, command, precept, grant, indult, declaration, will, decree and prohibition.
Should anyone, however, presume to commit such an act, he should know that he will incur the wrath of Almighty God and of the Blessed Apostles Peter and Paul.
"[3] Soon after the publication of this 1907 table, Pope Pius X made a general revision of the rubrics of the calendar, the result of which (with a few additions by Pope Pius XI) can be seen in General Roman Calendar of 1954.
John XXIII's General Roman Calendar of 1960 reduced the number of celebrations and completely abandoned the ranking as Doubles, Simples, etc.