Something random I learned in Korea
February 14: Girls treat the boys
March 14: 'White Day' where boys treat the girls
April 15: 'Black Day'--the day when all the single folks (and all those who don't do anything on 2/14 and/or 3/14) go eat 자 장 면 (Jajangmyun), the black noodles mentioned here.
November 11 or 11/11: Pepero Day
People exchange boxes of Pepero, long, thin biscuits dipped in chocolate or yogurt flavoring, on this day. Why 11/11? Pepero's long, stick shape looks like the date--thus a holiday was born.