1. calendar era; year numbering system used by a calendar
Wikipedia definition
2. Calendar eraA calendar era is the year numbering system used by a calendar. For example, the Gregorian calendar numbers its years in the Western Christian era (the Coptic and Ethiopic churches have their own Christian eras, see below). The instant, date, or year from which time is marked is called the epoch of the era. There are many different calendar eras. In antiquity, regnal years were counted from the ascension of a monarch.
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