Korean calendar
From 1945 to 1961 in South Korea, Gregorian calendar years were counted from the start of Gojoseon in 2333 BC (regarded as year one). These Dangi (단기 / 檀紀) years were 4278 to 4294. This numbering was often used unofficially with the Korean lunar calendar before 1945. It has only sometimes been used after 1961, mostly in North Korea before 1997.