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

Other days

kiss a brunette

Kiss A Brunette Day
polyamory

Polyamory Day
bubble bath

Bubble Bath Day
offer

Offer Day
bounce

Bounce Day
gum

Gum Day
bow tie

Bow Tie Day
ormille

Ormille Day
boyfriend

Boyfriend Day
lisp

Lisp Day