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

Other days

pumpkin

Pumpkin Day
donate your hair

Donate Your Hair Day
ruby

Ruby Day
offer

Offer Day
bow tie

Bow Tie Day
china

China Day
self appreciation

Self Appreciation Day
hiv awareness

Hiv Awareness Day
gum

Gum Day
boyfriend

Boyfriend Day