Thanksgiving became a fixed national holiday on the fourth Thursday of November in 1941.
Before that law, U.S. Thanksgiving dates were set through presidential proclamations and generally fell on the last Thursday of November. Abraham Lincoln established a recurring national observance during the Civil War, proclaiming Thanksgiving for the final Thursday in November in 1863. That practice continued for decades, but the date was not yet permanently fixed by federal law.
President Franklin D. Roosevelt created confusion in 1939 by moving Thanksgiving to the next-to-last Thursday in November. November had five Thursdays that year, and Roosevelt hoped an earlier holiday would give merchants more time for Christmas shopping. Critics called the competing observances “Franksgiving,” and some states followed different dates.
Congress resolved the dispute in December 1941, when Roosevelt signed legislation fixing Thanksgiving on the fourth Thursday of November, beginning in 1942. The holiday can therefore fall between November 22 and November 28. The year 1863 marks the modern national tradition, but 1941 marks the permanent legal date.