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

Other days

ask out your crush

Ask Out Your Crush Day
slime

Slime Day
offer

Offer Day
artists

Artists Day
brow

Brow Day
china

China Day
stress awareness

Stress Awareness Day
lash

Lash Day
boy friend

Boy Friend Day
tulip

Tulip Day