Chuseok

"Chuseok is one of the largest and most widely celebrated holidays in South Korea. This holiday is a time of happiness and reconnecting as families gather, chat, and have great feasts. The primary reason for Chuseok in South Korea is to honor ancestors and deceased relatives, but the holiday also serves the purpose of keeping the family together in a time when work and other obligations may separate people. Traditionally, Chuseok also allowed South Koreans to celebrate the Autumn harvest after a season of hard work. Chuseok is held on the 15th day of the 8th month on the lunar calendar, or the fall equinox."

http://publicholidays.asia/south-korea/chuseok/