Oops, it doesn't look like 'swim a lap sit on a lap day' is a national day..

Other days

bow tie

Bow Tie Day
offer

Offer Day
camera

Camera Day
lisp

Lisp Day
unicorn

Unicorn Day
cat girl

Cat Girl Day
hiv awareness

Hiv Awareness Day
kale

Kale Day
bubble bath

Bubble Bath Day
china

China Day