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

Other days

carpenters

Carpenters Day
bounce

Bounce Day
one

One Day
blanket fort

Blanket Fort Day
comfy

Comfy Day
pumpkin

Pumpkin Day
self appreciation

Self Appreciation Day
donate your hair

Donate Your Hair Day
nae nae

Nae Nae Day
believe

Believe Day