Complex sentence: Some Koreans think of it as the earliest Korean state and of Dangun as the ancestor of Koreans, and from 1948 until December 1961, the Republic of Korea officially, 1948-09-25 reckoned years by adding 2333 to the Common Era year.
Split into simpler sentences: Some Koreans think of it as the earliest Korean state and of Dangun as the ancestor of Koreans. From 1948 until December 1961, the Republic of Korea officially, 1948-09-25 reckoned years by adding 2333 to the Common Era year.