re: (OK, so maybe not so) Crazy polifactoid - JFK was only 7 years and change older than

On a somewhat related note - the only Presidents older than any previous President (and generally it is only the immediate predecessor unless otherwise noted) are:

Andy Jackson

William Henry Harrison

Zachary Taylor

James Buchanan (who was older than both Fillmore and Pierce, his 2 immediate predecessors)

Andy Johnson

Grover Cleveland

Taft (his predecessor, Teddy R was the youngest man to serve as President)

Woodrow Wilson (the first time it happened twice in a row, and Wilson, like Buchanan, was older than both Teddy and Taft)

LBJ, Nixon and Ford (the troika), while all served in birth order, were all older than JFK (the youngest man elected President, Teddy R became President upon the death of McKinley)

Reagan ( - older than the FIVE previous Presidents)

Bush 42 - Older than Carter by a few months

Bush 44 - Older than Clinton by a few weeks

Trump - older than Bush 44 and Clinton by a few weeks

Biden - older than Clinton, Bush 44 and Trump by ~3.5 to 4 years