The date and location of the first Thanksgiving celebration is a topic of modest contention. Though the earliest attested Thanksgiving celebration was on September 8, 1565 in what is now Saint Augustine, Florida, the traditional "first Thanksgiving" is venerated as having occurred at the site of Plymouth Plantation, in 1621.
Today, Thanksgiving is celebrated on the second Monday of October in Canada and on the fourth Thursday of November in the United States. Thanksgiving dinner is held on this day, usually as a gathering of family members.(Tomado de "wikipedia")