Most are pilfered from
Holidays For Everyday: An excuse to celebrate everyday!. The holidays listed on that site come from a variety of sources, most notably the Library of Congress and the National Special Events Registry. Some (like Gorilla Suit Day and Talk Like a Pirate Day) were conceived and promoted by individuals and aren't recognized by any authority, but I included them here because they're fun. Just my idea of what a nation of clowns might celebrate
