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

Other days

fiancee

Fiancee Day
blanket fort

Blanket Fort Day
china

China Day
reading

Reading Day
slime

Slime Day
bow tie

Bow Tie Day
cat girl

Cat Girl Day
lisp

Lisp Day
stud

Stud Day
offer

Offer Day