Thanksgiving Date Calculator

Thanksgiving is what calendar programmers call a floating holiday defined by an nth-weekday-of-month rule, which makes it fully deterministic without any astronomical input. The United States observance is the fourth Thursday of November, codified in federal law at 5 U.S.C. 6103, and Canada observes the second Monday of October. The algorithm finds the weekday of the first of the month, computes the offset to the first occurrence of the target weekday using modulo 7 arithmetic, then adds seven days for each additional occurrence. Because November has either four or five Thursdays, the fourth Thursday can only fall between 22 and 28 November; Canadian Thanksgiving is similarly bounded between 8 and 14 October. Two derived dates follow mechanically in the United States. Black Friday is the day after Thanksgiving, so it ranges from 23 to 29 November, and Cyber Monday is four days after Thanksgiving, ranging from 26 November to 2 December. Neither is a statutory holiday. The important limitation of this calculation is historical rather than mathematical: the fourth-Thursday rule only applies from 1942 onward. Between 1863 and 1938 the observance followed the last Thursday of November, which coincides with the fourth Thursday only in years where November has four Thursdays, and the years 1939 to 1941 were genuinely irregular because different states observed different dates. Any date this tool produces for a year before 1942 should therefore be read as the fourth Thursday, not as the day actually observed at the time.

The 1621 harvest feast shared by Plymouth colonists and the Wampanoag is the celebration usually cited as the origin, though days of thanksgiving were a familiar Protestant practice long before and were proclaimed irregularly by colonial governments and by the Continental Congress. George Washington issued the first national Thanksgiving proclamation on 3 October 1789, setting Thursday 26 November of that year, but the observance did not become annual. Sarah Josepha Hale, editor of Godey's Lady's Book, campaigned for roughly three decades for a fixed national holiday, and Abraham Lincoln responded with a proclamation on 3 October 1863, in the middle of the Civil War, establishing the last Thursday of November as a national day of thanksgiving. The modern rule dates from a dispute. In 1939 November contained five Thursdays, and Franklin D. Roosevelt, urged by retailers who wanted a longer Christmas shopping season during the Depression, moved the holiday from the last Thursday to the next-to-last. Roughly half the states refused, some observed both dates, and the press dubbed the earlier date Franksgiving. Congress ended the confusion with House Joint Resolution 41, signed on 26 December 1941, which fixed the holiday as the fourth Thursday of November from 1942. Canada's holiday developed separately from harvest observances and from a thanksgiving Parliament proclaimed in 1879; after being moved repeatedly, it was fixed to the second Monday of October by parliamentary proclamation on 31 January 1957.