I have recently discovered that South Korea celebrates all kinds of weird, arbitrary holidays.
1月14日 :: Diary Day (다이어리데이)
2月14日 :: Valentine's Day（밸런타인데이）
3月14日 :: White Day（화이트데이）
4月14日 :: Black Day (블랙데이)
5月14日 :: Rose Day（로즈데이이）/Yellow Day（옐로데이）
6月14日 :: Kiss Day（키스데이）
7月14日 :: Silver Day（실버데이）
8月14日 :: Green Day（그린데이）
9月14日 :: Photo Day（포토데이）/Music Day（뮤직데이）
10月14日 :: Wine Day（와인데이）
11月11日 :: PEPERO Day（빼빼로데이
11月14日 :: Orange Day、Movie Day （오렌지 데이）,（영화의 날）
12月14日 :: Hug Day（허그데이）
I wonder why Koreans celebrate so many days. It seems especially difficult for couples if they have to think about presents every month and finding new ways to celebrate.
Comments
I also agree with how weird and arbitrary some of these holidays may seem. Most of these holidays I wasn't even aware of! However, Pepero Day and White Day are the two main holidays that I remember celebrating. I thought it was odd when girls were required to give presents to the guys first on White Day. As for Pepero Day, it was just a nice excuse to eat Pepero!
I know from experience that at least half of those aren't really practiced. The one's that are really big are Valentine's Day, White Day, and PEPERO Day out of your list. Some of them aren't even known among native Koreans. Koreans do tend to make a day out of almost anything and its something you choose to practice so no pressure!! Something thats not on your list thats big in Korea are the family days including Mothers, Fathers, and Children's day. Hope this helped!