Seniors in
Motion
Lynn Haven Senior Center
905
Pennsylvania Ave, Lynn Haven, Florida 32444 (850)277-2730
Why is Leap Year Necessary?
Leap years are added to the calendar to keep it working properly. The 365 days of the annual calendar are meant to match up with the solar year. A solar year is the time it takes the Earth to complete its orbit around the sun - about one year. But the actual time it takes for the Earth to travel around the sun is in fact a little longer. - about 365 1/4 days (365 days, 5 hours, 48 minutes, and 46 seconds, to be precise). So, the calendar year is a touch shorter than the solar year. (Sandy's note - How did they ever figure that out??) Doesn't seem like much of a difference, but after a few years, those extra quarter days in the solar year begin to add up. After 4 years, the 4 extra quarter days would make the calendar fall behind the solar year by about a day. Over the course of a century, the difference between the solar year and the calendar year would become 25 days! Instead of summer beginning in June, it wouldn't start until nearly a month later in July. Kids looking forward to summer vacation know - calendar or no calendar - that's way too late! So, every 4 years, a leap day is added to the calendar to allow it to catch up to the solar year.
Hmmmm. It's not that simple. The math seems to work out beautifully when you add an extra day to the calendar every 4 years to compensate for the extra quarter of a day. However, the solar year is just about 365 1/4 days long, but not exactly! The exact length of a solar year is actually 11 minutes & 14 seconds per year. this time really starts to add up: after 128 years, the calendar would gain an entire extra day. So, the leap year rule, "add a leap year every 4 years" was a good rule, but not good enough.
Calendar Correction Part II. To rectify the situation, the creators of our calendar (the Gregorian calendar, introduced in 1582) decided to omit leap years every 400 years. This would shorten the calendar year every so often & rid it of the annual excess of 11 minutes & 14 seconds. So, in addition to the rule that leap year occurs every 4 years, a new rule was added: a century year is not a leap year unless it is evenly divisible by 400. This rule manages to eliminate 3 leap years every few hundred years. (Aren't you glad you don't have to keep track of all this?)
Smooth sailing for the next 3,300 years! This ingenious correction worked beautifully in bringing the calendar & the solar year in harmony, pretty much eliminating those pesky extra 11 minutes & 14 seconds. Now, the calendar year and the solar year are just about a half a minute off. At that rate, it takes 3,300 years for the calendar year and solar year to diverge by a day. Whew! Interesting, but probably more information than you wanted!
What are the chances of being born on a leap year? About 1 in 1500.
How many people were born on leap day? About 187,000 in the US and 4 million worldwide.
When is the birthday party? If you are born on a Leap Year, do you get your driver's license on February 28th or March 1st? It is an ambiguous question that is decided by each state. Most states, however, consider March 1st the official day. For instance, the Michigan Vehicle Code states that people born on February 29th "are deemed to have been born on March 1st".