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

Other days

fiancee

Fiancee Day
nail polish

Nail Polish Day
lisp

Lisp Day
bow tie

Bow Tie Day
frozen yogurt

Frozen Yogurt Day
cat girl

Cat Girl Day
one

One Day
cursing

Cursing Day
unicorn

Unicorn Day
gum

Gum Day