You may have heard that 2020 is a leap year meaning we’ll add a day to the calendar this February. So, why do we have leap years?
To start, a year is defined as one complete rotation around the sun. We grew up learning this to be 365 days, right? Well, it’s close, but not quite.
*One rotation takes about 365.24 days. So if you do the math it turns out it takes about 5.8 hour more every year to do one complete rotation around the sun.
Now as times goes on that extra time adds up and if we didn’t have leap days like this month, in 100 years our calendar would be off by 24 days.
To make up for that we add a full calendar day every for year which should now solve our problem, right? Well, we are getting closer. If we head back to the calculator we find we’re still off by about 11 minutes too long every year. If we look 100 years down the road our time will be off by about 18 hours.
So how do we solve this problem? It’s called leap year hop scotch. At the beginning of each century a leap year is skipped to help bring the calendar back into alignment, unless that century is divisible by 400, much like the year 2000.
Even after doing all of these crazy tricks the calendar still doesn’t exactly match the Earth’s trip around the sun, but it’s much closer and it would take over 3,300 years for the calendar to be off by a day. Odds are all of you watching this right now won’t have to worry about that problem.