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

Other days

buddy

Buddy Day
stress awareness

Stress Awareness Day
fiancee

Fiancee Day
pick me

Pick Me Day
nae nae

Nae Nae Day
ride the wind

Ride The Wind Day
bow tie

Bow Tie Day
lisp

Lisp Day
youth

Youth Day
camera

Camera Day