Oops, it doesn't look like 'retweet pinned tweets day' is a national day..

Other days

lisp

Lisp Day
donate your hair

Donate Your Hair Day
buddy

Buddy Day
hannah

Hannah Day
polyamory

Polyamory Day
ormille

Ormille Day
brow

Brow Day
coffee

Coffee Day
ruby

Ruby Day
boy friend

Boy Friend Day