Epoch

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An epoch is a chosen moment used as the start of a calendar era. It marks the point from which time is counted, usually tied to a clear event or turning point.

Examples:
- Japan counts years from when the current emperor ascends the throne, with that accession year as Year 1.
- China used a similar idea before 1912, counting from the emperor’s accession; for example, 1911 was Year 3 of the Xuantong era.
- After the Republic was founded in 1912, the republican era began, and Taiwan still often uses the republican era for dating.
- The People's Republic of China uses the common era calendar starting in 1949.
- Canada uses regnal years for Acts, a system it inherited from the UK, so it is currently 4 Charles III. This regnal system was used in the UK and England from 1307 until 1963, when the Gregorian calendar was adopted.