koreanfestivals1-1, Exercise 1: Three kinds of day

Model answer:

National day (국경일): a day celebrating an event considered joyous to Korea. Four major ones were provided for by a 1949 law (Independence Declaration Day, Constitution Day, Liberation Day, National Foundation Day); Hangul Day became the fifth in 2005.
National flag raising day (국기게양일): all the national celebration days, plus Memorial Day (half staff) and Armed Forces Day, under Article 8 of the National Flag Law; raising the taegukgi is promoted.
Public holiday (공휴일): a day off for the general working population, on which employers are legally required to pay employees; based on the Regulations on Holidays of Public Agencies.

Public holiday and tradition are not the same: the categories are legal ones, and the article shows many are commemorations of modern events (for example the 1949 national celebration days, set after the 1948 government), while a custom can exist without being a public holiday.

Source: Wikipedia, Public holidays in South Korea.