Article II of the Constitution states that once elected, a president serves a term of four years. It does not, however, define how many terms a president can serve. George Washington set the precedent that two terms was enough. This unwritten rule was followed until FDR was elected for a third term, and then for a fourth term. Congress decided that an amendment was needed to return to the precedent set by Washington. Now, a president can serve only two terms, or a maximum of ten years.
The text of this amendment begins, “No person shall be elected to the office of the President more than twice, and no person who has held the office of President, or acted as President, for more than two years of a term to which some other person was elected President shall be elected to the office of President more than once.”