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

Other days

unicorn

Unicorn Day
mean girls

Mean Girls Day
self care

Self Care Day
lash

Lash Day
one

One Day
artists

Artists Day
first love

First Love Day
ruby

Ruby Day
chocolate milkshake

Chocolate Milkshake Day
pumpkin

Pumpkin Day