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

Other days

book

Book Day
ruby

Ruby Day
bow tie

Bow Tie Day
singles

Singles Day
bonang

Bonang Day
martini

Martini Day
my little pony

My Little Pony Day
eat what you want

Eat What You Want Day
tulip

Tulip Day
frozen yogurt

Frozen Yogurt Day