Gaecheonjeol is a public holiday in South Korea

Public holidays in South Korea

Public holidays in South Korea each belong to one or more of three categories:*National Celebration Day *National Flag Raising Day *Public Day Off...

 on 3 October. Also known by the English name National Foundation Day, this holiday celebrates the creation of the state of Gojoseon

Gojoseon

Gojoseon was an ancient Korean kingdom. Go , meaning "ancient," distinguishes it from the later Joseon Dynasty; Joseon, as it is called in contemporaneous writings, is also romanized as Chosŏn....

 (ancient Korea

Korea

Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...

) founded by Dangun Wanggeom in the year 2333 BC.

Origin

Gaecheon (or "Opening of Heaven") refers to 3 October B.C. 2457, the date when Hwanung

Hwanung

Hwanung is an important figure in the mythological origins of Korea. He plays a central role in the story of Dangun Wanggeom , the legendary founder of Gojoseon, the first kingdom of Korea. Hwanung is the son of Hwanin , the "Lord of Heaven"...

 (환웅) descended from heaven to live with mankind.

The harvest ceremony was celebrated in each Korean kingdoms; Yeonggo (영고) of Buyeo

Buyeo

Buyeo can mean:*Buyeo kingdom, a kingdom located in today's North Korea and southern Manchuria from around the 2nd century BC to 494 AD*Buyeo County, a county in South Chungcheong Province, South Korea, and one-time capital of the ancient kingdom of Baekje...

, Mucheon (무천) of Yemaek

Yemaek

Yemaek were an ethnic group who dwelt in Manchuria and the Korean Peninsula. They had ancestral ties to various Korean kingdoms including Gojoseon, Gori , Buyeo, Goguryeo, Baekje, Okjeo, Dongye, Yangmaek and Sosumaek , and is believed to be one of the ancient tribes that were formed into the...

, Gyeeum (계음) of Mahan

Mahan

Mahan may refer to:*Mahan confederacy, chiefdoms in ancient Korea*Mahan, Iran, a city in Kerman province*Mahan District, an administrative subdivision of Kerman Province*Iranian male first name*Mahan Air, an airline based in Kerman province...

 and Byeonhan, Dongmaeng (동맹) of Goguryeo

Goguryeo

Goguryeo or Koguryŏ was an ancient Korean kingdom located in present day northern and central parts of the Korean Peninsula, southern Manchuria, and southern Russian Maritime province....

, Palgwanheoi (팔관회) of Silla

Silla

Silla was one of the Three Kingdoms of Korea, and one of the longest sustained dynasties in...

.

In 1909, Gaecheonjeol was enacted as a national holiday. The festival is held annually.
At first, Gaecheonjeol had been celebrated on 3 october on lunar calendar but it has been celebrated on 3 october on solar calendar since 1949.