Tabular Islamic leap cycle
About the Tabular Islamic leap cycle
The arithmetical, or tabular, Islamic calendar adds a day to Dhu al-Hijjah in 11 years of every 30, giving years of 354 or 355 days and a mean month very close to the astronomical lunation. Astronomers and historians use it to convert dates, although most Muslim communities set religious dates by moon sighting or national calendars.
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