Islamic Calendar and Muslim Holy Days Index
To understand Muslim holidays, it is helpful to understand their calendar system. The Islamic calendar started in the Western year 622 A.D. Its starting point was the date on which Muhammad and his closest companions moved from Mecca to Medina , known as the Hijra.
The Muslim calendar is lunar-based, comprising of 12 months and a year of 354 days. Each month can be either 29 or 30 days long. Because the lunar year is shorter than the solar year, Muslim holy days cycle backwards through the Western calendar. The Islamic lunar calendar differs from the moon's actual cycle by one day every 2,570 years, which means that it is only a little bit less accurate than the solar calendar.
Originally the months were regulated based upon the sighting of the moon, but today more sophisticated astronomical calculations are employed. The months are known a