About CalendarDB
CalendarDB is a reference guide to 108 entries on calendars and the reckoning of time. It covers 31 calendar systems, 19 eras and year counts, 14 calendar reforms and national adoptions of the Gregorian calendar, the leap rules and cycles that keep calendars aligned with the Sun and Moon, the twelve Gregorian months and seven weekdays, and festivals whose dates are set by calendar rules.
What each entry contains
Every page records the entry's type, its cultural tradition, its astronomical basis (solar, lunar, lunisolar or a pure count), the date it was introduced or took effect where that is known, a key figure such as year length or the number of days skipped, and a short description of how it works and why it matters. Where an origin date is unknown or disputed, as for many ancient calendars, the field is left blank rather than guessed. Dates before 1582 are given in the Julian calendar unless stated as proleptic Gregorian.
Sources
Facts were checked against standard references including the papal bull Inter gravissimas, the British Calendar (New Style) Act 1750, ISO 8601, national legislation such as the Iranian calendar law of 1925 and the Indian national calendar of 1957, and encyclopaedia articles on individual calendars. Errors reported are corrected as they are found.
Entries by type
- Calendar Systems: 31
- Eras and Year Counts: 19
- Months of the Year: 14
- Calendar Reforms and Adoptions: 14
- Calendar-Based Observances: 12
- Calendar Cycles and Leap Rules: 11
- Days of the Week: 7