Islamic calendar

The Islamic calendar or Muslim calendar (also called 'Hijri calendar') is the calendar used to date events in predominantly Muslim countries, and used by Muslims everywhere to determine the proper day on which to celebrate Muslim holy days. It is a purely lunar calendar having 12 lunar months in a year of about 354 days. Because this lunar year is about 11 days shorter than the solar year, Muslim holy days, although celebrated on fixed dates in their own calendar, usually shift 11 days earlier each successive solar year, such as a year of the Gregorian calendar. Islamic years are also called Hijra years because the first year was the year during which the Hijra occurred—Muhammad's emigration from Mecca to Medina. Thus each numbered year is designated either H or AH, the latter being the initials of the Latin anno Hegirae (in the year of the Hijra).

Pre-Islamic calendar

The predecessor to the Islamic calendar was a lunisolar calendar in that it used lunar months but was also kept synchronized with the seasons by the insertion of an additional, intercalary, month when required. Whether the intercalary month (Nasi) was added in the spring like that of the Hebrew calendar or in autumn is debatable. It is assumed that the intercalary month was added between the twelfth month (the month of the pre-Islamic Hajj) and the first month (Muharram) of this pre-Islamic year. The two Rabi' months denote grazing and the modern Meccan rainy season (only slightly less arid than normal), which would promote the growth of grasses for grazing, occurs during autumn. These imply a pre-Islamic year beginning near the autumnal equinox. But the rainy season after which these months are named may have been different when the names originated (before Muhammad's time) or the calendar may have been imported from another region which did have such a rainy season. On the other hand, Muhammad forbade the intercalary month (released the calendar from the seasons) near the end of his life, which implies a pre-Islamic year beginning near the vernal equinox because that is when the modern lunar year began during his last year.

Related Topics:
Lunisolar calendar - Intercalary month - Hebrew calendar - Hajj - Muharram - Autumnal equinox - Vernal equinox

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