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| Leap Year |
What is a leap year?
With leap years is added to the calendar, an additional day: the 29th February. For a leap year has not 365 but 366 days. As often as leap years are determined by fixed rules: All numbers divisible by four years of smooth, are leap years, as are all divisible by 400-year figures. Smoothly divisible by 100-year figures are only leap years if they are also divisible by 400.
Why there are leap years?
For a calendar, there are natural measures of time: the year as the orbital period of the Earth around the sun, the month as the orbital period of the moon around the earth. This day, which is set daily by the sun's path. The big problem is that all these figures are not round. The year has 365.2422 days on average, between two new moons are 29.5306 days. Rules for leap years to correct this situation but complicated figure.
When was leap year - and how do they work?
Each calendar is odd because the natural time, a compromise measure. Smallest inaccuracies can have big consequences in the long run. Already knew that the Babylonians in the third millennium before Christ, and invented leap months. The Egyptians placed 238 BC to a leap day every fourth year. The Roman emperor Julius Caesar in 45 BC led a solar calendar with a simple leap year rule - every three years - one.
But even with this modernization of the calendar year was still about eleven minutes longer than the solar year. That added up to the 16th Century to ten days. To customize the calendar back to reality, Pope Gregory XIII decided. in 1582 these ten days simply fail and modernized the leap year rules again. In this way, 36524.25 days fall in a century. This is the natural time measurements very close. The still remaining minimal deviations from the solar year are now balanced by the occasional insertion of leap seconds.
