Thanksgiving Day is celebrated on the fourth Thursday of November. Before 1941, when the date was formalized, the day Thanksgiving was celebrated caused confusion, as some people celebrated the holiday on the last Thursday and some on the second-to-last Thursday of November.
President Franklin Roosevelt thought that celebrating Thanksgiving on the last Thursday of November would shorten the Christmas shopping season and hurt the recovery of the economy. He issued a proclamation that moved Thanksgiving to the second-to-last Thursday. Not all states liked this idea, and some decided to keep celebrating the holiday on the last Thursday of the month.
In 1941, to avoid having Thanksgiving on two days, Congress passed a resolution stating that Thanksgiving would always be on the fourth Thursday of November.