This Fourth of July, Americans will celebrate the adoption of the Declaration of Independence with picnics, parades and, of course, fireworks. It's a tradition that's been in place for more than 200 years — and for more than 200 years, it's been kind of wrong.

"It is the right day to celebrate the Declaration of Independence," author and historian Ray Raphael tells NPR's Guy Raz. "It is not the right day to celebrate the signing of the declaration or the right day to celebrate independence. The vote for independence was on July 2 — two days before — and the first signing of the declaration ... was not until August 2 — a month later."