Why Leap Years Matter for Your Exact Age

Every four years (with a few exceptions), February has 29 days instead of 28. That extra day exists to keep our calendar aligned with Earth's orbit around the sun.

For most of us, leap years don't change much: our birthday still arrives once a year. But over a long life, the extra days add up — a 70-year-old has lived through roughly 17 extra days because of leap years.

People born on February 29 ("leaplings") technically have a birthday only every four years. Most observe it on February 28 or March 1 in non-leap years, but their official age in years still increases each year on the calendar.