The U.S. Constitution is 225 years old, but some of the amendments are much younger.
Like, for instance, the 22nd Amendment. It turns 61 today, and sets an important limit for the president.
“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 the President more than one time.”
The Constitution Daily has the full history of the amendment, which passed in 1951 not long after Franklin Delano Roosevelt was elected to his fourth term in office.