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

Other days

self appreciation

Self Appreciation Day
lisp

Lisp Day
cursing

Cursing Day
bounce

Bounce Day
ponytail

Ponytail Day
bow tie

Bow Tie Day
artists

Artists Day
stress awareness

Stress Awareness Day
unicorn

Unicorn Day
pumpkin

Pumpkin Day