There's a saying that presidents age twice as fast while in office. If that's true, be sure to wish President Barack Obama a happy 54th birthday on Tuesday and then see how he and other presidents have aged while in office.
President Kennedy would be assassinated on Nov. 22, 1963, just two years and 10 months into his first term. His was the seventh-shortest term as president. He is shown here on July 11, 1963, at the age of 46.