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

Other days

ruby

Ruby Day
ask out your crush

Ask Out Your Crush Day
bounce

Bounce Day
first love

First Love Day
aloxolt

Aloxolt Day
lisp

Lisp Day
offer

Offer Day
ormille

Ormille Day
mean girls

Mean Girls Day
kale

Kale Day