February 29, 2008
Leap Year
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Updated February 29, 2008
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The Leap Day is used to keep the calendar year synchronized with the astronomical or seasonal year.
The Gregorian calendar is the most widely used calendar in the world today. It is the calendar we in the United States use today. This is a modification of the Julian calendar. The calendar was decreed by Pope Gregory XIII on February 24, 1582.
In our current Gregorian calendar, most years that are divisible by 4 are leap years. In which case, February has 29 days, versus the normal 28 days.
Why is this done?
The solar year is a little less than 6 hours longer than 365 days.
But, to throw a curve ball in there, the solar year is slightly less than 365.25 days. So, you'd think roughly every fourth year adding a day will compensate. Well, I mentioned a solar year is slightly less than 365.25, not exactly that amount. So, if the year is divisible by 100, there will be no leap year, unless it is divisible by 400. In which case, they are leap years.
Following that, the years 1600 and 2000 were leap years. But, 1700, 1800, 1900 were not.
The next two leap years divisible by 400 will be 2400 and 2800.
This Gregorian calendar was designed to keep the vernal equinox on or close to March 21. This keeps Easter (which falls on the Sunday after the 14th day of the Moon that fall on or after March 21.
This Gregorian calendar is not perfect. So any of you who will still be here in 8,000 years, you’ll notice the calendar is off by one day.
The Gregorian calendar is a modified version of the Julian calendar, developed by Julius Caesar in 46 b.c., and implemented in 45 b.c.
The difference between the Julian and Gregorian calendar is that the Gregorian calendar has three less leap days each 400 years than the Julian calendar.
For the true answer to the question, “How long is a year?”, you can say it is 365 days, 5 hours, 49 minutes and 12 seconds.
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