Today we've been given an extra day. Good? or Bad? It's good this year because it's a beautiful sunny day with temperatures near 60 degrees, but one leap year really messed me up. Three of our children were born on the 18th of some month. It made it really easy to remember their birthdays. Quinn was born on the 17th of March in 1980, which happened to be a leap year. Had it not been a leap year, he would have also been born on the 18th. Rats!
So why leap year? Well, in case you didn't know, it actually takes the earth 365 days + 5 hours, + 48 minutes, + 46 seconds to circle the sun. No big deal, but over time it begins to add up. So they created the Julian calender which added 1 day (4x5 hours + 48 minutes + 46 seconds) or approximately 24 hours every fourth year. Great, the problem is solved! Wait a minute! Every year the Julian calendar is about 11 minutes too long. No big deal, but over time . . . So, in 1582, Pope Gregory XII created the Gregorian calendar (used today) which says that every century year could only be a leap year if it was divisible by 400. So, the year 1900 was not a leap year, but the year 2000 was. The year 3000 will not be a leap year, but the year 4000 will be. Ok, so are we good to go? Not exactly. The Gregorian calendar puts the calendar year very close to the solar year, but it is still a tiny bit off. But it will take around 3000 years for this tiny difference to add up to an extra day, so astronomers have a few years to figure how how to deal with that problem.
It's a little mind-boggling, so just go out and enjoy this extra day, and let the mathematicians worry about the calendar!