Oops, it doesn't look like 'dahyun stan clown day' is a national day..

Other days

lisp

Lisp Day
bow tie

Bow Tie Day
comfy

Comfy Day
pick me

Pick Me Day
hannah

Hannah Day
youth

Youth Day
nae nae

Nae Nae Day
ride the wind

Ride The Wind Day
self appreciation

Self Appreciation Day
aloxolt

Aloxolt Day