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

Other days

ormille

Ormille Day
bow tie

Bow Tie Day
camera

Camera Day
lisp

Lisp Day
boy friend

Boy Friend Day
slime

Slime Day
bounce

Bounce Day
embarrass your best friend

Embarrass Your Best Friend Day
boba

Boba Day
one

One Day