Regnal year

A regnal year is a year of the reign of a sovereign, from the Latin regnum meaning kingdom, rule. Regnal years considered the date as an ordinal, not a cardinal number. For example, a monarch could have a first year of rule, a second year of rule, a third year of rule, and so on, but not a zeroth year of rule. Applying this ancient epoch system to modern calculations of time, which include zero, is what led to the debate over when the third millennium began. Regnal years are "finite era names", contrary to "infinite era names" such as Christian era, Jimmu era, Juche era, and so on. Egyptian chronology In ancient times, calendars were counted in terms of the number of years of the reign of the current monarch. Reckoning long periods of time required a king list. The oldest such reckoning is preserved in the Sumerian king list. Ancient Egyptian chronology was also dated using regnal years. The Zoroastrian calendar also operated with regnal years following the reform of Ardashir I in 3rd century. The Canon of Kings is a list that dates the reigns of various Babylonian, Persian, Macedonian, Egyptian, and Roman monarchs, that was used by ancient astronomers as a way to date astronomical phenomena. The Liberian Catalogue is a similar list of popes of Early Christianity, that was used to date early events in the religion's history. Chinese era nameKorean era nameJapanese era name and Vietnamese era name Regnal years were generally used for year marking in the Chinese cultural sphere before the advent of era names. In China, the continuous use of era names began in 140 BC, during the rule of the Emperor Wu of Han. Prior to that, years were usually marked as regnal years of the monarch. Since 140 BC, era names served as titles for the purpose of numbering and identifying years. Era names were used for over two millennia by Chinese emperors and are still used in Japan. The Lanfang Republic era, Republic of Formosa era and Republic of China calendar are systems adapted from the traditional era name system, but they are not effectively era names.