Chronological Cycles for year 2021
The papal bull Inter gravissimas also includes six appendices, or “canons”, which were intended to explain the terms below:
- Canon 1: Concerning the 19-year cycle of the Golden Number
- Canon 2: Concerning the epact and the new moon
- Canon 3: The Solar cycle (or the 28-year cycle of Dominical letters)
- Canon 4: Dominical letters (Sunday letters)
- Canon 5: Indictions
- Canon 6: Moving holidays (Easter and other holidays)
These terms form the foundations of the year. Chronological signs, characteristic marks, and other unique church numbers found in old calendars are now considered obsolete. These terms were originally taken from the Julian calendar, but over time saw considerable updates, with many of their calculations modified (e.g. epacts, Dominical letters, the determination of Easter). For the remaining terms (Golden number, solar cycle, indictions) that are used in the Gregorian calendar, their relevance has waned over time, becoming less important. In foreign sources, only the first five terms are taken as the chronological cycles, while calculating moving holidays, such as Easter Sunday, can be derived from them. Below you can find the values for a given year for both calendars:
| Golden number | 8 |
| Solar cycle | 14 |
| Indiction | 14 |
| Dominical letter | D |
| Alexandrian epact | 17 |
| Easter Sunday | Apr 19 |
| Easter Sunday (in gregorian calendar) | May 2 |
| Dominical letter | C |
| Gregorian epact | 16 |
| Easter Sunday | Apr 4 |