Japanese era name
The Japanese era name (Japanese: 元号, Hepburn: gengō, "era name") or nengō (年号, year name), is the first of the two elements that identify years in the Japanese era calendar scheme. The second element is a number which indicates the year number within the era (with the first year being "gan (元)") meaning "origin, basis", followed by the literal "nen (年)" meaning "year". Era names originated in 140 BCE in Imperial China, during the reign of the Emperor Wu of Han. As elsewhere in the Sinosphere, the use of era names was originally derived from Chinese imperial practice, although the Japanese system is independent of the Chinese, Korean, and Vietnamese era name systems. Unlike its other Sinosphere counterparts, Japanese era names are still in official use.