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| | WWU Planetarium - Leap Year Rules |
 | | This was the basis of the Julian calendar, introduced by Julius Caesar in 46 B.C. In this case the calendar year is longer than the tropical year by about 0.0078 days. |
 | | However, around 10 BC, it was found that the priests in charge of computing the calendar had been adding leap years every three years instead of the four decreed by Caesar (Vardi 1991, p. |
 | | Leap years were therefore 45 BC, 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, 9 BC, 8 AD, 12 AD, and every fourth year thereafter (Tøndering), until the Gregorian calendar was introduced (resulting in skipping three out of every four centuries). |
| www.wwu.edu /depts/skywise/leapyear.html (623 words) |
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