To the existing distinction between major and ordinary or minor doubles, Pope Clement VIII added two more ranks, those of first-class or second-class doubles. Some of these two classes were kept with octaves. This was still the situation when the 1907 article Ecclesiastical Feasts in the Catholic Encyclopedia was written. In accordance with the rules then in force, feast days of any form of double, if impeded by "occurrence" (falling on the same day) with a feast day of higher class, were transferred to another day. Pope Pius X simplified matters considerably in his 1911 reform of the Roman Breviary. In the case of occurrence the lower-ranking feast day could become a commemoration within the celebration of the higher-ranking one. Until then, ordinary doubles took precedence over most of the semidouble Sundays, resulting in many of the Sunday Masses rarely being said. While retaining the semidouble rite for Sundays, Pius X's reform permitted only the most important feast days to be celebrated on Sunday, although commemorations were still made until Pope John XXIII's reform of 1960. The division into doubles (of various kinds) semidoubles and simples continued until 1955, when Pope Pius XII abolished the rank of semidouble, making all the previous semidoubles simples, and reducing the previous simples to a mere commemoration in the Mass of another feast day or of the feria on which they fell (see General Roman Calendar of Pope Pius XII). Then, in 1960, Pope John XXIII issued the Code of Rubrics, completely ending the ranking of feast days by doubles etc., and replacing it by a ranking, applied not only to feast days but to all liturgical days, as I, II, III, and IV class days. The 1969 revision by Pope Paul VI divided feast days into "solemnities", "feasts" and "memorials", corresponding approximately to Pope John XXIII's I, II and III class feast days. Commemorations were abolished. While some of the memorials are considered obligatory, others are optional, permitting a choice on some days between two or three memorials, or between one or more memorials and the celebration of the feria. On a day to which no obligatory celebration is assigned, the Mass may be of any saint mentioned in the Roman Martyrology for that day. Observed by Roman Catholics and some Anglicans on August 15, which is the same as the Eastern and Orthodox feast of the Dormition, the end of the earthly life of the Virgin Mary and, for some, her bodily Assumption into heaven, is celebrated.