Oops, it doesn't look like 'change your twitter handle to something spooky day' is a national day..

Other days

hot chocolate

Hot Chocolate Day
bow tie

Bow Tie Day
self care

Self Care Day
ruby

Ruby Day
mean girls

Mean Girls Day
one

One Day
tulip

Tulip Day
hannah

Hannah Day
self appreciation

Self Appreciation Day
lost sock memorial

Lost Sock Memorial Day