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What Is Leap Year? Leap Day Explained

Feb. 28, 2012
Leap Year, Leap Day

Tomorrow, Feb. 29, is a rare occurrence. Only in a leap year do we have a Feb. 29, otherwise known as leap day. Generally speaking, leap year and leap day only come around every four years ... but why?

Having a leap day helps the calendar year stay in step with the seasonal year.

In the calendar we use in the United States -- the Gregorian calendar -- most years that can be evenly divided by four are leap years, wherein we have a Feb. 29, versus a "common year," in which February only has 28 days. This compensates for the approximately six hours less that the calendar year has versus a solar year (the actual time it takes the Earth to journey around the Sun).

However, if a year is evenly divisible by 100, it is not a leap year, unless it is also evenly divisible by 400. For example, 2100 will not be a leap year, but 2000 (divisible by 400 evenly) was, in fact, a leap year.

In the arts, Frederic, from the Gilbert & Sullivan operetta "The Pirates of Penzance," is famously born on leap day, but is obligated to serve the Pirate King until his 21st birthday. This means in real time he must serve until he is 84 years old -- that is, until he has seen 21 leap years pass. Yikes!

Source: (c) 2012. All rights reserved.

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