Oops, it doesn't look like 'wear a show shirt as a real shirt day' is a national day..

Other days

cursing

Cursing Day
stress awareness

Stress Awareness Day
tell a fairytale

Tell A Fairytale Day
cuddle up

Cuddle Up Day
tell ur crush you like them

Tell Ur Crush You Like Them Day
self appreciation

Self Appreciation Day
china

China Day
promposal

Promposal Day
nae nae

Nae Nae Day
believe

Believe Day