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

Other days

ponytail

Ponytail Day
blanket fort

Blanket Fort Day
boyfriend

Boyfriend Day
youth

Youth Day
lisp

Lisp Day
martini

Martini Day
polyamory

Polyamory Day
ormille

Ormille Day
ask out your crush

Ask Out Your Crush Day
boy friend

Boy Friend Day