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

Other days

ruby

Ruby Day
martini

Martini Day
stress awareness

Stress Awareness Day
brow

Brow Day
gum

Gum Day
one

One Day
chocolate milkshake

Chocolate Milkshake Day
unicorn

Unicorn Day
bounce

Bounce Day
hannah

Hannah Day