ATLANTA — This weekend will bring a bonus day that has some people wondering why February 29th appears only once every four years.
2020 is a leap year. If you were born on February 29th you get to celebrate on your actual birthday this year.
The answer requires a trip around the sun.
It takes approximately 365-days for the earth to circle the sun. That’s why a calendar year is typically 365 days. The issue is that the earth’s trip around the sun is not exactly 365 days.
“It actually takes closer to 365 ¼ days,” says Andrew Novick of the National Institute of Standards and Technology. “You can’t have a calendar with a quarter of a day.”
Hundreds of years ago, astronomers discovered that the journey takes closer to 365 days and six hours. While six hours may not seem like a lot, if the calendar is off that much each year, it will be off an entire day in four years.
SO, around 45 B.C. the Romans added a day once every four years creating the leap year.
However, it turns out they overcompensated just a tad. Adding a day every four years is about 11-minutes too much. So, we now skip the leap year three times every four hundred years.
“Typically, we skip the leap year at the turn of the century,” says Novick. “But since it’s only necessary three times every four centuries, we had a leap year in February of 2000.”
If not for all of these adjustments, our calendar would slowly shift away from the seasons as we know them. Eventually, we would be wearing heavy jackets in August.