Islamic calendar - Hijrah

The Islamic calendar or Muslim calendar or Hijri calendar (Arabic: التقويم الهجري‎; at-taqwīm al-hijrī; Persian: تقویم هجری قمری ‎taqwīm-e hejri-ye qamari; Turkish: Hicri Takvim) is a lunar calendar used to date events in many predominantly Muslimcountries, and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. It is a 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, Islamic 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 yearsbecause the first year was the year during which the Hijra occurred—Islamic prophet Muhammad's emigration from Mecca toMedina. 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).

The current Islamic Year is 1430 AH, from approximately December 28, 2008 (evening) to December 17, 2009 (evening).

Taken from: http://en.wikipedia.org