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

Other days

bonang

Bonang Day
buddy

Buddy Day
cat girl

Cat Girl Day
kiss a ginger

Kiss A Ginger Day
polyamory

Polyamory Day
self appreciation

Self Appreciation Day
ruby

Ruby Day
lash

Lash Day
brow

Brow Day
hannah

Hannah Day