There's a saying that presidents age twice as fast while in office. With Thursday marking President Barack Obama's 55th birthday, take a look back over the past 60 years of U.S. presidents and judge for yourself how much the office aged them.
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.