Thanksgiving Day Thanksgiving Day is a very important traditional holiday in America. On the fourth Thursday of each November, families and friends gather together for the occasion to celebrate with a traditional turkey dinner, usually in the mid-afternoon. Thanksgiving Day originated as a celebration of the year's harvest and is similar to the Mid-Autumn Festival in China. This American tradition started in 1621 before the United States of America was established. It was a huge celebration for a hard-earned harvest in the first year after the first group of immigrants arriving in the New World.