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

Other days

kiss a ginger

Kiss A Ginger Day
hoodie

Hoodie Day
cuddle up

Cuddle Up Day
my little pony

My Little Pony Day
artists

Artists Day
slime

Slime Day
brow

Brow Day
girl friend

Girl Friend Day
bow tie

Bow Tie Day
promposal

Promposal Day