Although the 1787 U.S. Constitution does not foresee a limitation of the president's mandate, it seems that George Washington's voluntarily leaving the function of President after his second term in office had established a rule which grew into a constitutional custom, and no other president ran for a third time after that; except for Franklin Roosevelt, who during the WWII (before the U.S. joined the war) ran for a third, and in 1944 for a fourth mandate. After the war however, the practice initiated by George Washington was enshrined in the Constitution with the 22nd amendment to the U.S. Constitution, adopted on 27 February 1951. This amendment was supplemented with a reference which foresees that in the case of death or resignation of the President, the vice-president will take over the function, and if that person serves as president for more than two years, he can be re-elected only once, i.e. the person who served as president for more than six years cannot be re-elected in the next four years.