Oops, it doesn't look like 'buljangnan day' is a national day..

Other days

azonto is acceptable

Azonto Is Acceptable Day
pick me

Pick Me Day
donate your hair

Donate Your Hair Day
blanket fort

Blanket Fort Day
stud

Stud Day
ruby

Ruby Day
bounce

Bounce Day
lisp

Lisp Day
slime

Slime Day
ponytail

Ponytail Day