The old Korean calendar tells the phases of the moon and the day in the solar year, like other older calendars of other East Asian countries. Dates are calculated from Korea's meridian. Important dates are based in Korean culture.
The Gregorian calendar officially began to be used in 1896. The dates of older important Korean events are still based on the old calendar. The most important date in Korea today is Seollal, the first day of the Korean calendar's New Year. Other important events include Daeboreum (the first full moon phase, also referred to as Boreumdaal), Dano (spring) and Chuseok (autumn), and Samjinnal (beginning of spring). Other minor events based on the old Korean calendar include Yudu (summer), and Chilseok (monsoon season).
The old Korean calendar comes from the old Chinese calendar. The Korean calendar said what its years were by using Korean era names from 270 to 963. Then Chinese era names with Korean era names were used a few times until 1894. In 1894-1895, The calendar based on the moon was used with years numbered from the beginning of the Joseon Dynasty in 1392.
The Gregorian calendar began to be used on 1 January 1896, with Korean era name "Geonyang (건양 / 建陽, "adopting solar 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.
- Pyeon, Prof. M. Y. The Folkloric Study of Chopail (Buddha's Birthday). Seoul: Minsokwon, 2002.