What day was the star-spangled banner written?

The Star Spangled Banner was written by Francis Scott Key, a lawyer who was dining aboard a British ship with an American Prisoner Exchange Agent, trying to secure the release of his friend. He was on board the ship the night of the British bombardment of Fort McHenry in Baltimore on September 13, 1814. The Fort lasted all through the night, and on September 14th, the Americans took down the tattered storm flag and raised a larger one. Key was so filled with pride that he wrote the poem, then called "The Defence of Fort McHenry