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

Other days

donate your hair

Donate Your Hair Day
nae nae

Nae Nae Day
bow tie

Bow Tie Day
aloxolt

Aloxolt Day
polyamory

Polyamory Day
unicorn

Unicorn Day
pick me

Pick Me Day
cursing

Cursing Day
my little pony

My Little Pony Day
believe

Believe Day