Japanese regnal years

Japanese regnal years number years from the start of an emperor’s reign, rather than using the era name alone. The first regnal year begins on the accession date.

Japanese era name: A Japanese calendar designation associated with an emperor’s reign, such as Reiwa or Heisei. Regnal years count within the reign identified by this name.
Chinese era name: A reign- or event-based designation used to identify years in traditional Chinese calendars. Chinese era naming influenced the historical conventions adopted in Japan.
Japanese imperial calendar: A calendar convention that identifies years by the Japanese emperor’s reign and associated era. It uses regnal-year counts in official and ceremonial date references.
Gregorian year numbering: The numbering of years in the Gregorian calendar from its traditional epoch. It advances continuously rather than restarting with each Japanese reign.
Japanese calendar: The system of calendars and date conventions used in Japan. Regnal-year numbering is one way Japanese dates express years.
Japanese era: A period of Japanese history named for an era designation, often associated with an emperor’s reign. Regnal years developed within Japan’s broader era-based chronology.
Japanese public documents: Official records and forms issued or maintained by Japanese public authorities. Many forms record dates using an era and its regnal-year number.
Japanese era year: A year number counted from the beginning of a Japanese era, such as Reiwa 1. It is closely related to regnal years, though the terms emphasize different parts of the notation.
Japanese era calendar: A Japanese year-numbering system that resets to year one when a new era begins. Its era-based year count is the framework in which regnal years are expressed.
Taihō Code: An early eighth-century Japanese legal code that organized government and adopted continental institutions. Its era-name system helped establish year designation practices in Japan.

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