Oops, it doesn't look like 'do a grouch a favor day' is a national day..

Other days

gum

Gum Day
brow

Brow Day
lisp

Lisp Day
law

Law Day
kiss a ginger

Kiss A Ginger Day
promposal

Promposal Day
buddy

Buddy Day
get funky

Get Funky Day
tulip

Tulip Day
healing

Healing Day