For a little bit of history, learn that the Thanksgiving we know came about in 1941 as a boost to the economy:
From the book of knowledge (wikipedia):
Thanksgiving in the United States, much like in Canada, was observed on various dates throughout history. The dates of Thanksgiving in the era of the Founding Fathers until the time of Lincoln had been decided by each state on various dates. The first Thanksgiving celebrated on the same date by all states was in 1863 by presidential proclamation. The final Thursday in November had become the customary date of Thanksgiving in most U.S. states by the beginning of the 19th century. And so, in an effort by President Abraham Lincoln (influenced by the campaigning of author Sarah Josepha Hale who wrote letters to politicans for around 40 years trying to make it an official holiday), to foster a sense of American unity between the Northern and Southern states, proclaimed the date to be the final Thursday in November.
It was not until December 26, 1941 that the unified date changed to the fourth Thursday (and not always final) in November—this time by federal legislation. President Franklin D. Roosevelt, after two years earlier offering his own proclamation to move the date earlier, with the reason of giving the country an economic boost, agreed to sign a bill into law with Congress, making Thanksgiving a national holiday on the fourth Thursday in November.