Today is the day, back in 1863 when President Lincoln declared the first official Thanksgiving celebration by the nation would take place on November 26, 1863. The fourth Thursday of November was officially recognized by the United States as a national day of thanks. This came on the heels of the victory at Gettysburg.
Thanksgiving was officially celebrated on the fourth Thursday until Franklin D. Roosevelt changed it to the third Thursday of November in 1939 to help an ailing country get those extra shopping days in between Thanksgiving and Christmas. Congress didn’t much like that and it was moved back to the fourth Thursday of the month.