koreanfestivals1-2, Exercise 2: National Foundation Day and the celebration days

Model answer:

According to the Samguk Yusa, Dangun founded Gojoseon on the 3rd day of the 10th lunar month in 2333 BC. Today South Koreans celebrate National Foundation Day on 3 October of the Gregorian calendar "for convenience sake" (the article's wording, with no source given). So a legendary lunar date has been fixed to a Gregorian date by modern choice.

The four national celebration days of the 1949 law: Independence Declaration Day (1 March), Constitution Day (17 July), Liberation Day (15 August) and National Foundation Day (3 October). Hangul Day (9 October) was added as the fifth in 2005.

Source: Wikipedia, Public holidays in South Korea.