George Washington
At the end of his second term, Washington retired for personal and political reasons, fatigued and disgusted with personal attacks, and to assure a truly contested presidential election could be held. He did not feel bound to a two-term limit, but his retirement ultimately set precedent. The two-term limit to the presidency was formalized with the 1951 adoption of the Twenty-second Amendment to the United States Constitution. Washington is often credited with setting the principal of a two-term presidency, but it was Thomas Jefferson who first refused to run for a third term on political grounds.
Twentieth Amendment to the United States Constitution
The Twentieth Amendment (Amendment XX) to the United States Constitution moved the beginning and ending of the terms of the president and vice president from March 4 to January 20, and of members of Congress from March 4 to January 3. It also has provisions that determine what is to be done when there is no president-elect. The Twentieth Amendment was adopted on January 23, 1933.