In the United States, Thanksgiving occurs on the fourth Thursday in November and has been celebrated at this time since 1939. Prior to then, Thanksgiving was celebrated on the last Thursday of November.
Thanksgiving dates back to 1621, when colonists in Plymouth, Mass., held a three-day festival of thanks for a good harvest. For more than 200 years, different colonies and states held days of thanksgiving, but it wasn’t until 1863 that it became an official national holiday, designated as such by President Lincoln. Canadians have officially celebrated Thanksgiving as a national holiday since 1879, and the Canadian holiday has been on the second Monday in October since 1957.