Question: When was the last time korea was united?
Disambiguated questions and answers: question: When was the last time korea was united as measured by the time that the PRK was outlawed in the South?
When was the last time korea was united as measured by the time that the committees were co-opted in the North?
answer: December 12, 1945
February 1946
Natural Questions answer: in 1945 (from the Wikipedia article "History of Korea")