When we talk about Thanksgiving in school, there tends to be an impression left that we celebrate the holiday the same way it has been celebrated all the way back to the Pilgrims. But in reality, the modern celebration of Thanksgiving evolved very slowly and in many fits and starts.
"Thanksgiving" celebrations - celebrations where one gave thanks to God - were proclaimed in pre-Revolutionary times after various events, generally as harvest festivals to thank God for crops. During the Revolutionary War, first the Continental Congress began the practice of proclaiming a formal "Thanksgiving" and later George Washington proclaimed one for the troops to celebrate the victory at Saratoga. However, these celebrations could be in Spring, Winter, Summer, or any time that politics made one convenient. This practice was followed by the first presidents (Washington and Adams) and when the presidents stopped proclaiming it, most state governors took up the tradition by proclaiming days of thanks for their respective states. But again, few fell in Autumn and it was rare for two states to share the same date for thanksgiving.
It was only during the Civil War that President Lincoln, inspired by a series of editorials written by Sarah Josepha Hale, declared the last Thursday in November to be the national day of Thanksgiving. And later Franklin D. Roosevelt changed this to the next-to-last Thursday in November. Finally, to avoid confusion with various state calendars, Congress in 1941 declared the "fourth Thursday in November" would be the official day of Thanksgiving.
Who thought something as simple as giving thanks to God for the blessings of the nation would be so complicated to work out?