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

Other days

fiancee

Fiancee Day
donate your hair

Donate Your Hair Day
china

China Day
hiv awareness

Hiv Awareness Day
gum

Gum Day
stress awareness

Stress Awareness Day
coffee

Coffee Day
kiss a brunette

Kiss A Brunette Day
lash

Lash Day
one

One Day