In 1968, Congress passed the Monday Holidays Act, which moved the official observance of Washington's birthday from Feb. 22 to the third Monday in February. Some reformers had wanted to change the name of the holiday as well, to Presidents' Day, in honor of both Lincoln and Washington, but that proposal was rejected by Congress, and the holiday remained officially Washington's Birthday.
But in 1971, when the Act went into effect, President Nixon proclaimed the holiday as Presidents' Day, to commemorate all past presidents, not just Lincoln and Washington. This idea was never intended or authorized by Congress; nevertheless, it gained a strong hold on the public consciousness.