Martyrologium Romanum

The Roman Martyrology (Latin: Martyrologium Romanum) is the official martyrology of the Catholic Church. Its use is obligatory in matters regarding the Roman Rite liturgy, but dioceses, countries and religious institutes may add to it duly approved appendices. It provides an extensive but not exhaustive list of the saints recognized by the Church.

In 1582, Pope Gregory XIII decreed a revision of the Julian calendar, creating a new system, now called, after him, the Gregorian calendar. The Roman Martyrology was first published in 1583. A second edition was published in the same year. The third edition, in 1584, was made obligatory wherever the Roman Rite was in use.

The main source was the Martyrology of Usuard, completed by the "Dialogues" of Pope Gregory I and the works of some of the Fathers, and for the Greek saints by the catalogue known as the Menologion of Sirlet. Its origins can be traced back to the Martyrologium Hieronymianum, which was originally based on calendars of Roman, African and Syrian provenance, but to which were gradually added names of many saints from other areas, resulting in a number of duplications, fusions of different saints into one, and other mistakes.

Very soon, in 1586 and again in 1589, revised editions were published with corrections by Caesar Baronius along with indications of the sources on which he drew, and in 1630 Pope Urban VIII issued a new edition. 1748 saw the appearance of a revised edition by Pope Benedict XIV, who personally worked on the corrections: he suppressed some names, such as those of Clement of Alexandria and Sulpicius Severus, but kept others that had been objected to, such as that of Pope Siricius. Subsequent changes until the edition of 2001 were minor, involving some corrections, but mainly the addition of the names of newly canonized saints.

...
Wikipedia