Happy Thanksgiving is a popular expression people use to mark the celebration of the Thanksgiving Day holiday. Thanksgiving is celebrated primarily in the United States on the fourth Thursday of November of each year. Family members often use this occasion to get together and share a big feast prepared by the head of household. The feast almost always centers on the roast turkey. The exact origin of the holiday is unknown, but it generally thought to be related to the traditional harvest celebrations brought by settlers to North America from Europe.