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

Other days

bow tie

Bow Tie Day
unicorn

Unicorn Day
african immigrant and refugee hiv and hep awareness

African Immigrant And Refugee Hiv And Hep Awareness Day
cuddle up

Cuddle Up Day
martini

Martini Day
lumpy rug

Lumpy Rug Day
raise awerness of zeus

Raise Awerness Of Zeus Day
slime

Slime Day
stress awareness

Stress Awareness Day
hot chocolate

Hot Chocolate Day