What have Italian composer Rossini and American rapper Ja Rule got in common? A number of possible answers may leap to mind here, but the one I’m looking for is that the two musicians were both born on a date that is mysteriously elusive: 29 February. Except that 2012 is a leap year, and so this year the estimated 5 million or so leaplings, leapers, or leap-year babies around the world actually get to blow out the candles on the cake for their quadrennial celebration. During the intervening common years, however, the timing of their birthday festivities depends on the laws of whichever land they’re in. In New Zealand, a leapling’s official birthday is deemed to be 28 February, whereas in Britain it’s 1 March. If you timed it right, you could fly from one country to the other for the world’s longest birthday.