Since it takes Earth approximately 365 ^1/4 days to orbit the sun, an extra day’s worth of time accumulates every four years. In a leap year, February receives an extra day to compensate for the difference between the astronomical year and the calendar year.
If no adjustment were made, the calendar and the seasons would drift apart By 24 days every 100 years. The plan of adding a day every four years was devised by the Egyptians. The Romans created a standard leap day, February 29, in 46 B.C.
 Adding one day per four years didn’t perfectly correct the problem, however, because Earth orbits in II minutes and 14 seconds less than 365 ^1/4 days. A correction, established in 1582, adds a leap day only to century years divisible by 400.Thus 2000 was a leap year, but 2100, 2200 and 2300 will not be a leap year.


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