The February 14, 1961 Instruction of the Congregation for Rites on the application to local calendars of Pope John XXIII's motu proprio Rubricarum instructum of July 25, 1960 decreed that "the feast of 'Saint Anacletus', on whatever ground and in whatever grade it is celebrated, is transferred to April 26, under its right name, 'Saint Cletus'. The Roman Martyrology mentions the Pope in question only under the name of "Cletus". The Annuario Pontificio gives both forms, as alternatives. Eusebius, Saint Irenaeus, Saint Augustine and Optatus all suggest that both names refer to the same individual. On the other hand, the Liberian Catalogue and the Liber Pontificalis both state that Anacletus and Cletus are two different persons.
The name "Cletus" in Ancient Greek means "one who has been called", and "Anacletus" means "one who has been called back". St Cletus/Anacletus was traditionally said to have been a Roman, and to have been pope for twelve years. The Annuario Pontificio states: "For the first two centuries, the dates of the start and the end of the pontificate are uncertain." It gives the years 80 to 92 as the reign of Pope Cletus/Anacletus. Other sources give the years 77 to 88. Tradition has it that this Pope divided Rome into twenty-five parishes. One of the few surviving records concerning his papacy mentions him as having ordained an uncertain number of priests.
The Tridentine Calendar had on 26 April the feast day of Saint Cletus, honoured jointly with Saint Marcellinus, and on 13 July the feast day of Saint Anacletus. In 1960, Pope John XXIII, while keeping the 26 April feast, which mentions the saint under the name given him in the Canon of the Mass, removed that of 13 July. Use of this 1960 calendar, which is included in the 1962 edition of the Roman Missal, continues to be authorized under the conditions indicated in the motu proprio Summorum Pontificum; but the 26 April feast also has been removed from the General Roman Calendar since 1969.