What do the three calendar models cover?
The pre-1955 choice uses 1954 as its last full baseline before the simplified rubrics took effect on January 1, 1956, and adds the two feasts first kept in 1955 under the older rubrics: the Queenship of Mary on May 31 and St. Pius X on September 3. It does not claim that every year from 1911 through 1954 had an identical calendar. The 1962 Roman Missal choice applies the Code of Rubrics promulgated in 1960 and required from January 1, 1961. The current choice uses the General Roman Calendar, updated through February 2026.
The pre-1955 and 1962 choices are universal Roman calendar projections for the civil dates entered; the current choice is the calendar of the dioceses of the United States. None is an archival copy of the annual Ordo printed for a particular place.
Does the calendar include diocesan or national feasts?
The current calendar includes the proper calendar of the dioceses of the United States, with Epiphany, Ascension, and Corpus Christi on Sunday; the Ascension is kept on Thursday in the provinces of Boston, Hartford, New York, Omaha, and Philadelphia. The engine does not add diocesan, monastic, religious-order, or community propers, and the pre-1955 and 1962 calendars have no national propers.
What does a row in the results mean?
Each civil date has one principal result. Optional celebrations are listed as choices. Other losing candidates remain unclassified unless a source and rule establish their disposition. An unclassified candidate should not be read as a commemoration or transfer.
The pre-1955 model resolves every day fully under the 1954 rubrics: the office of the day with its rite (double of the first or second class, greater double, double, semidouble or simple) and the colour of its Mass, followed by the commemorations made at Lauds or Mass in the order the rubrics prescribe. Feasts that are impeded and transferred appear on the day they are kept. The rite of a Sunday or a day within an octave is semidouble, as in the Breviary.
The 1962 model resolves every day fully under the Code of Rubrics of 1960 and the Calendarium of the 1962 Missal: the office of the day with its class and colour, followed by the commemorations admitted at Lauds and Mass in the order the rubrics prescribe. Impeded feasts of the first class appear on the day to which they are transferred; feasts that the rubrics omit in a given year are named in the notes.
How are today and date ranges handled?
The opening comparison uses the civil date and time zone reported by your device. A selected date range is inclusive. Downloaded files contain that full selected range, even when the onscreen table has a text filter applied.
What has the calendar been checked against?
The pre-1955 model is tested day by day against two printed diocesan Ordos with the same calendar pattern as the current years: the Gniezno Ordo for 1953 for every day of 2026, and the Włocławek Ordo for 1937 for every day of 2027. Polish and diocesan feasts are removed, and the 1937 Ordo is brought forward to 1954 by the decrees that followed it (the Immaculate Heart of Mary on 22 August and Saint John Leonardi on 9 October). Each fixture day cites the Ordo page it was read from. It is also tested against every cell of the occurrence table printed in the 1942 Desclée Breviary, read from the page image, and against the Gniezno Ordos for 1947 through 1954 for calendar patterns the current years do not have: Christmas, the Epiphany and 2 November on a Sunday, very early and very late Easter, leap years, and the transfer of the Annunciation and Saint Joseph.
The 1962 model rests on the Latin text of the 1960 Code of Rubrics (Acta Apostolicae Sedis 52, 1960) and the Calendarium of the 1962 typical edition of the Missal. It is tested against the printed Gniezno Ordos for 1961 through 1969, which apply the same rubrics, and against the Missal’s own table of movable feasts for 1960 through 2011.
The current model applies the Universal Norms on the Liturgical Year and the Calendar (1969), nn. 5, 14, 15, 44, 59, and 60, the 1998 notification on the Immaculate Heart of Mary, the 2018 decree on Mary, Mother of the Church, and the proper calendar of the dioceses of the United States. It is checked day by day against the USCCB liturgical calendars for 2026, 2027, and 2028.
The automated evidence set also contains six complete-year fixtures preserving 2,192 cited civil dates. They include a 1952 diocesan Ordo, a universal 2007 Ordo using the 1962 books, the 1970 general-calendar schema, and official United States calendars for 2024 through 2026. Local entries stay visible in the research but are excluded from universal-calendar defect claims.
What are the known limits?
The current model does not show the Liturgy of the Hours. The 1962 model does not show Vespers (concurrence) or votive Masses. The pre-1955 model does not show Vespers (concurrence), the ninth lesson, or the resumption of an impeded Sunday Mass on a weekday. Complete primary-source coverage is also thin for 1955, 1956, 1960, 1962, and the early postconciliar years.
For liturgical use, compare the result with an approved Ordo for the jurisdiction, community, and year concerned.