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

Other days

nae nae

Nae Nae Day
brow

Brow Day
self appreciation

Self Appreciation Day
bow tie

Bow Tie Day
azonto is acceptable

Azonto Is Acceptable Day
tulip

Tulip Day
bounce

Bounce Day
cursing

Cursing Day
china

China Day
carpenters

Carpenters Day