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.
And here's a look at President George H.W. Bush taking a last walk around the White House grounds with first lady Barbara Bush on Jan. 20, 1993. Bush is 68 years old in this photo.