Regnal year dating
Reckoning long periods of times required a king list.The oldest such reckoning is preserved in the Sumerian king list.
Overseas Chinese used Longfei (龍飛) or Tianyun (天運).The tradition of Korean era names survives in the North Korean Juche calendar, with Juche year 1 being 1912 the year of the birth of Kim Il-sung.The official Japanese system or Nengō numbers years from the accession of the current emperor, regarding the calendar year during which the accession occurred as the first year.A regnal year is a year of the reign of a sovereign, from the Latin regnum meaning kingdom, rule.The oldest dating systems were in regnal years, and considered the date as an ordinal, not a cardinal number.
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The Chinese eras or Nian Hao were used sporadically from 156 BC and continuously from 140 BC.