Chuseok, one of Korea's most well-known traditional days, is coming up. People of Korea are looking forward to this event very much, since there's a whole week of national holidays. But what is Chuseok, and why are people celebrating this big event?   Chuseok is a national holiday of Korea, celebrated every year on August 15th of the lunar calendar. You might ask, why use the lunar calendar? That is because until the early 20th century, the lunar calendar was widely used thro