The official Independence Day of South Korea is celebrated on 15th August, though the actual day of independence was on August 13th 1948. The official date which is 15th August, 1945 was not the day the South Koreans attained final autonomy from Japan.
It was only on 13th August, 1948, that South Korea was fully liberated from any sort of outside administration. For political reasons, first President of the country I Seung-man, chose 15th August, instead of 13th as the official Independence Day of South Korea.
The Independence Day of South Korea commemorates the freedom from decades of Japanese occupation and the formation of the South Korean republic. Subsequent to the 1905 Taft-Katsura agreement, the Japanese took control of Korea in the year 1910. They restricted the political freedom of the Koreans and also took control over the Korean economic and communications systems. The Japanese further attempted to assimilate the people of Korea into their culture.
There are records of a number of Korean resistance movements for economic and social independence. The biggest demonstration of such resistance was the March First Independence Movement of 1919.
The Japanese surrendered after the Hiroshima and Nagasaki were hit by atomic bombs in the beginning of August 1945, which ended the World War II, and Korea achieved its independence.
The Independence Day of South Korea is declared an official national holiday countrywide. The day is celebrated with festivities and parades. The National flag is hoisted to honor the great Koreans who fought for the country's freedom.