Oops, it doesn't look like 'sports stadium on day' is a national day..

Other days

lisp

Lisp Day
aloxolt

Aloxolt Day
mean girls

Mean Girls Day
ruby

Ruby Day
self appreciation

Self Appreciation Day
cat girl

Cat Girl Day
kiss a ginger

Kiss A Ginger Day
hannah

Hannah Day
one

One Day
stud

Stud Day