As Biden turns 80, Americans ask 'What's too old?'

Joe Biden turns 80 on Sunday, making him the first octogenarian president in US history. He is set to celebrate his birthday with a brunch hosted by his wife, Jill, a celebration that got an extra lift this weekend with his granddaughter's wedding at the White House on Saturday.

With Biden already the oldest person to serve as president, the 2024 race for the White House is shaping up to be uncharted territory for the US.

The nearly 250-year old democracy celebrates youth, but millions of Americans - including presidents are now working well beyond the traditional retirement age of 65.

Ronald Reagan was 77 when he left the White House, but Biden would be 86 by the time a second four-year term ends, should he win it. His leading potential Republican opponent, Donald Trump, would be 82 when he left office if he won in 2024.