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

Other days

coffee

Coffee Day
bubble bath

Bubble Bath Day
polyamory

Polyamory Day
bounce

Bounce Day
offer

Offer Day
eat what you want

Eat What You Want Day
self care

Self Care Day
martini

Martini Day
slime

Slime Day
unicorn

Unicorn Day