Hangeul Day (Korean Language day) is observed on 9 October. It marks the invention and proclamation of the Korean alphabet in 1446.
King Sejong the Great who was the fourth monarch of the Joseon Dynasty, devised and proclaimed the Korean alphabet in the 15th century.
The celebration of the proclamation as a holiday began in the mid 1920's as attempt to preserve the Korean alphabet while under Japanese colonial rule of Korea (1910-1945), during which time Japanese was the country's official language.
Originally the day was celebrated according to the Lunar calendar, then on 28 October following some discussion about using the Gregorian or Julian (in use in 1446) calendar. In 1940 an historical document from the 15th century was found which revealed the true date of the proclamation to have been on 9 October 1446.
Following liberation from Japanese rule after the end of the Second World war, Hangeul Day was designated an official holiday in 1949.
It was excluded from the list of public holidays in 1991 after pressure from major employers on the grounds there were too many holidays, which would have an adverse impact on the national economy.
Hangeul Day regained some of its status in 2005 when it was designated as a national day of celebration.
In 2013 it regained its position as a national holiday.
In North Korea, the day is called Chosun-gul Day and celebrated on 15 January, which is the date in 1444 which refers to the date of the creation of the new language, not its proclamation.