Some basic facts:
Ronald Reagan was born on Feb 6, 1911.
He was sworn in as President on Jan 20, 1981 (69 years 349 days of age) and again on Jan 20, 1985 (73/349). The second occasion was a record for the oldest person to be sworn in as President, though it was for his second term.
Now, it appears that the next President (who will be sworn in on Jan 20, 2021) will be ONE OF the following:
Donald Trump (Jun 14, 1946)
Joseph Biden (Nov 20, 1942)
Bernard Sanders (Sep 8, 1941)-even before Pearl Harbour!
Trump was 70/220 when he was sworn in on Jan 20, 2017. That makes him the oldest to be sworn in as President for the FIRST time (unlike Reagan in 1985). And if he wins this time, he will be sworn in on Jan 20, 2021 at a record of 74/220, several months older than Reagan’s 73/349 in 1985.
And Biden will be still older on that day if he is elected: 78/61.
Sanders will be even older: 79/134.
Long live gerontocracy! as Mahathir Mohamad, Robert Mugabe and others such as Morarji Desai would have said.
So youngsters such as Pete Buttegieg and Tulsi Gabbard would need to be about 40 years older if they are to be taken seriously.
Meanwhile Jimmy Carter (Oct 1, 1924 and President in 1977-81) looks on in his 95th year.