New Delhi, Feb. 29 -- What happens once every four years and can bring anything from unbridled joy to thoughts of inescapable curses? No, not the World Cup. A leap year, of course, and with it the day of February 29. Those born on this particular date - some five million people worldwide, known as Leaplings or Leapers - face the dilemma of choosing which day to celebrate their birthday on during non-leap years. But they can also look forward to a special milestone when the date actually appears in the calendar, as is the case in 2024.

In Ireland, February 29 is known as Bachelor's Day, or Lady's Privilege, and has traditionally been viewed as a day when women may propose to men, based on the legend of Saint Bridget and Saint Patrick.

It...