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

Other days

unicorn

Unicorn Day
bow tie

Bow Tie Day
cursing

Cursing Day
first love

First Love Day
bounce

Bounce Day
boyfriend

Boyfriend Day
lisp

Lisp Day
martini

Martini Day
singles

Singles Day
hiv awareness

Hiv Awareness Day