This year is leap year, which adds an extra day to the calendar tacked on to the end of February. Coincidentally this occurs in the same year as the presidential elections. So why do we have leap years?

A year is supposed to be the time it takes for Earth to go around the sun. But it falls short. About 400,000 miles short. This happens each year and after four years we adjust by adding the 29th day to February. During this “leap day” Earth will travel nearly 1.6 million miles in its path around the sun making up for the shortages in the previous three years. A leap day keeps our man made calendars in sync with the seasons and thus the reason for the leap year.

Tomorrow, January 3, Earth will be at its closest point to the sun, moving through space at 67,779 miles per hour. The speed varies depending on how the other planets and the moon are lined up as they each contribute a small braking tug due to gravity.

To be precise, a year is 365 days, 5 hours, 48 minutes and 46 seconds long – the actual length of time it takes Earth to complete its orbit around the sun. Since the year is not quite 365 and a quarter days long, after several hundred years a further adjustment would need to be made to the calendar. To help account for this quirk, a leap day is not added in years ending in “00” unless (there are always exceptions to any rule of course!) a century is evenly divisible by 400. The year 2000 was a leap year but the year 2100 will not be.