Oops, it doesn't look like 'Wear a Show Shirt as a Real Shirt day' is a national day..

Other days

Eat What You Want Day

African Immigrant And Refugee Hiv And Hep Awareness Day

Frozen Yogurt Day

Law Day

Lumpy Rug Day

Hot Chocolate Day

Tell A Fairytale Day

Boyfriend Day

Cuddle Up Day

Stud Day