Washington's Birthday is a United States federal holiday celebrated on the third Monday of February in honor of George Washington, the first President of the United States. It is commonly but erroneously known as Presidents Day (sometimes spelled Presidents' Day or President's Day). As Washington's Birthday or Presidents Day, it is also the official name of a concurrent state holiday celebrated on the same day in a number of states.
Titled Washington's Birthday, a federal holiday honoring George Washington was originally implemented by an Act of Congress in 1879 for government offices in the District of Columbia (20 Stat. 277) and expanded in 1885 to include all federal offices (23 Stat. 516). As the first federal holiday to honor an American citizen, the holiday was celebrated on Washington's actual birthday, February 22. On January 1, 1971, the federal holiday was shifted to the third Monday in February by the Uniform Monday Holiday Act. This date places it between February 15 and 21, which makes the name "Washington's Birthday" in some sense a misnomer, since it never occurs on Washington's actual birthday, either February 11 (Old Style ), or February 22 (New Style).
(... from Wikipedia on 2012-04-17 05:25:47)