HAPPY LEAP DAY!

[dakals]

Why Leap Years Are Used
This page provides the history of the leap year and the purpose it serves.
February 29, 2008
The year 2008 is a leap year. If you look at a 2008 calendar, you will see that February has five Fridays–the month begins and ends on a Friday. Between the years 1904 and 2096, leap years that share the same day of week for each date repeat only every 28 years. The most recent year in which February comprised five Fridays was in 1980, and the next occurrence will be in 2036. February 29, the leap day, has been associated with age-old traditions, superstitions and folklore.
What is a leap year?
A leap year is a year in which one extra day has been inserted, or intercalated, at the end of February. A leap year consists of 366 days, whereas other years, called common years, have 365 days.
Which years are leap years?

In the Gregorian calendar, the calendar used by most modern countries, the following three criteria determine which years will be leap years:

1. Every year that is divisible by four is a leap year;
2. of those years, if it can be divided by 100, it is NOT a leap year, unless
3. the year is divisible by 400. Then it is a leap year.

According to the above criteria, that means that years 1800, 1900, 2100, 2200, 2300 and 2500 are NOT leap years, while year 2000 and 2400 are leap years.

It is interesting to note that 2000 was somewhat special as it was the first instance when the third criterion was used in most parts of the world.

In the Julian calendar–introduced by Julius Caesar in 46 BC and patterned after the Roman calendar–there was only one rule: any year divisible by four would be a leap year. This calendar was used before the Gregorian calendar was adopted.
Why are leap years needed?
Leap years are needed to keep our calendar in alignment with the earth's revolutions around the sun.
Details
The Earth's motion around the sun
Note: The illustration is not to scale.

The vernal equinox is the time when the sun is directly above the Earth's equator, moving from the southern to the northern hemisphere.

The mean time between two successive vernal equinoxes is called a tropical year–also known as a solar year–and is about 365.2422 days long.

Using a calendar with 365 days every year would result in a loss of 0.2422 days, or almost six hours per year. After 100 years, this calendar would be more than 24 days ahead of the season (tropical year), which is not desirable or accurate. It is desirable to align the calendar with the seasons and to make any difference as insignificant as possible.

By adding a leap year approximately every fourth year, the difference between the calendar and the seasons can be reduced significantly, and the calendar will align with the seasons much more accurately.

(The term "day" is used to mean "solar day"–which is the mean time between two transits of the sun across the meridian of the observer.)
Is there a perfect calendar?

No calendars used today are perfect; they are off by seconds, minutes, hours or days every year. To make a calendar more accurate, new leap year rules have to be introduced to the Gregorian calendar, complicating the calculation of the calendar even more. It will, however, need some modifications in a few thousand years. As for the tropical year, it is approximately 365.242199 days, but varies from year to year because of the influence of other planets.
Name of calendar When introduced Average year Approximate error introduced
Gregorian calendar AD 1582 365.2425 days 27 seconds (1 day every 3,236 years)
Julian calendar 45 BC 365.25 days 11 minutes (1 day every 128 years)
365-day calendar - 365 days 6 hours (1 day every 4 years)
Lunar calendar ancient 12-13 moon-months variable

A calendar similar to the Julian calendar, with every fourth year earmarked as a leap year, was first introduced by King Ptolemy III of Egypt in 238 BC.

In ancient times, it was customary to have lunar (moon) calendars, with 12 and/or 13 months every year. To align the calendar with the seasons, the 13th month was inserted as a "leap month" every two or three years. Many countries, especially in Asia still use such calendars. Read more about Leap Year in Other Calendars.

Note: Many other calendars have been and still are used throughout the world

[coloradontexas]

thanks dakals, not that i ever wanted to know any of that, but it is interesting. one day you'll see me on jepordy and that will be the multi million dollar question. LOL

[dantama]

I guess all the babies born here today will have a messed up birthday schedule.

[coloradontexas]

didnt even think about that dan, crazy!!

[ringadingh]

There was more to it than I would have thought, interesting reading.

[audiogooroo]

My boss is a leap year baby, born on Feb 29, so he's like 16 today.

[ianicky]

Wow Dakals your a mind of usful information ::)
I supose you know that a woman can propose marrage to a man on this day, i only know this cause thats how my wife got me :( lol

................................WOW............... .......and to think I just thought it was February 29th.

In honor of the day, I 'leaped,' but not very high..............................yet! Heheheheh!

[davidjones1]

WOW! are you snowed in?
ride safe