I'm especially interested in solutions that will show that a large majority of the population of the planet will live through two such events in their normal lifespan

Well, without writing any code at all, I know of two that have already occurred during my lifespan.

• 1:23:45 6/7/89 (h:mm:ss d/m/yy), and
• 12:34:56 7/8/90 (hh:mm:ss d/m/yy)

Both of those are in "English" date format (I believe that m/d/y is "American" date format). Although, they are valid dates in either format, I guess.

Cheers,
Darren :)