A certain person lived for many years to a ripe old age, but [ Editor: ".

Perhaps he was an ancient Roman who was born on February 29 before
Augustus Caesar appropriated that day (except on leap years, which
previously had a Feb. 30 [ Editor: "Feb.30" in the original ]) to make his eponymous month as long as
Julius Caesar's?  Or something along these lines...  Other calendars
may have had a similar history.

-- Noam D. Elkies <elkies@math.harvard.edu> [ Editor: signed
   "elkies@math.harvard:edu" in the original ]

[ Editor: the story that Augustus took a day from February for his
month is generally regarded as a medieval invention (it goes back to
Sacrobosco in the 13th century); the Julian February never had 30
days. ]

Sweden, uniquely, made the switch from the Julian calendar to the
Gregorian by abolishing all leap years from 1700 to 1740 inclusive.
This means that a Swede born on 29th February 1660, for example, would
have had his ninth actual birthday at the age of 36, and no more unless
he lived to be 84.  This seems to fulfil the terms of the problem
perfectly.

I made my original answer so brief because I thought this was a bit
of an old chestnut.  I am interested to discover that it is not,
apparently, well-known in Sweden where it all happened.

-- Bob Newman <yaw74@dial.pipex.com>

Curious about the Sweden answer given to this puzzle, I checked the
"calendar FAQ" at http://www.quadrivium.com/FAQ/calfaq.htm.  Here is
an excerpt from their FAQ [ Editor: the FAQ's copyright block is
condensed to: Copyright (C) 1996 by Claus Tondering ]:

  Sweden has a curious history.  Sweden decided to make a gradual
  change from the Julian to the Gregorian calendar.  By dropping every
  leap year from 1700 through 1740 the eleven superfluous days would
  be omitted and from 1 Mar 1740 they would be in sync with the
  Gregorian calendar.  (But in the meantime they would be in sync with
  nobody!)

  So 1700 (which should have been a leap year in the Julian calendar)
  was not a leap year in Sweden.  However, by mistake 1704 and 1708
  became leap years.  This left Sweden out of synchronisation with
  both the Julian and the Gregorian world, so they decided to go
  *back* to the Julian calendar.  In order to do this, they inserted
  an extra day in 1712, making that year a double leap year!  So in
  1712, February had 30 days in Sweden.

  Later, in 1753 Sweden changed to the Gregorian calendar by dropping
  11 days like everyone else.

So actually, the answer that he was born in Sweden in the late [ Editor: "last" in
the original ] 17th century doesn't work.

-- Mike Soss <soss@cs.mcgill.ca> [ Editor: posted as
   soss@cs.mcgill.caNada, an anti-spam form ]