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

Other days

artists

Artists Day
hoodie

Hoodie Day
law

Law Day
eat what you want

Eat What You Want Day
brow

Brow Day
donate your hair

Donate Your Hair Day
nae nae

Nae Nae Day
camera

Camera Day
cuddle up

Cuddle Up Day
boba

Boba Day