Thanksgiving has been held on the fourth Thursday in November since 1941, which means that the date of the holiday shifts each year. The earliest Thanksgiving can occur is November 22; the latest is November 28. President Roosevelt changed Thanksgiving from the fourth Thursday to the third Thursday in November in 1939. However, this was not a very popular move. Native Americans in North America celebrated harvest festivals for centuries before a Thanksgiving federal holiday was formally established in the United States. Colonial services for these festivals date back to the late 16th century. The autumnal feasts celebrated the harvest of crops after a season of bountiful growth. The first national Thanksgiving celebration was observed in honor of the creation of the new United States Constitution ! In 1789, President George Washington issued a proclamation designating November 26 of that year as a “Day of Public Thanksgiving” to re...