Trump marks 80th birthday, now second octogenarian sitting president: 'Seemed to utterly defy age'

President Donald Trump turned 80 on Sunday, becoming only the second sitting U.S. president to reach octogenarian status in the Oval Office, leaving even his onetime political opponents marveling at his defying the effects of Father Time – even if his critics continue to share concerns they never had with the older former President Joe Biden, now 83.

"You don't have to wish me a happy birthday, because I'm not happy about that birthday that I'm having," Trump joked with Dr. Mehmet Oz, 66...