Happy Leap Day! Ever wonder why we have an extra day every four years?
According to NASA, it takes Earth 365.2422 days to make one revolution around the Sun. You will notice that the Gregorian calendar we use maxes out a year at 365 days, and not a moment more.
โThe rotation of the earth that causes 24-hour days does not evenly match up with the orbit of the earth around the sun, which gives us our 365-day year,โ says Mandy Scurry, a NASA/JPL Solar System Ambassador living in Newburgh, Indiana. Thus, a leap year โis not because someone miscalculated when making the calendar. Itโs basic orbital mechanics.โ
If an extra day every four years seems cumbersome, imagine the alternative.
โThe two donโt meet to make it a nice, neat number. To correct that, we add a day every four years, instead of adding six hours each year,โ Scurry says.
Leap years arenโt a new initiative. In 1582, Pope Gregory XIII adopted the Gregorian calendar and inaugurated the concept of adding one day every four years โjust to even things out a little bit,โ Scurry says.
The math has not always been simple. The pope dictated that all years that can be divided by four are leap years. An exception is century years, which must be divisible by 400 to be considered leap years. In this instance, while 2000 was a leap year, 2100 and 2200 will not be.
Convoluted or not, โThe whole point is to fix it so we can go on with our lives. We make adjustments so it doesnโt interfere with our daily lives,โ Scurry says. โThis is literally how we move around in the universe.โ
