The Islamic calendar , also known as the Hijri, Lunar Hijri, Muslim or Arabic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days.
It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the pilgrimage to Mecca.
The civil calendar of almost all countries where the religion is predominantly Muslim is the Gregorian calendar, with Syriac month-names used in the Levant and Mesopotamia (Iraq, Syria, Jordan, Lebanon and Palestine).
Notable exceptions to this rule are Iran and Afghanistan, which use the Solar Hijri calendar. Rents, wages and similar regular commitments are generally paid by the civil calendar.
The Islamic calendar employs the Hijri era whose epoch was established as the Islamic New Year of 622 AD/CE.
During that year, Prophet Muhammad (s) and his followers migrated from Mecca to Medina and established the first Muslim community (ummah), an event commemorated as the Hijra.
In the West, dates in this era are usually denoted AH (Latin: Anno Hegirae, "in the year of the Hijra") in parallel with the Christian (AD), Common (CE) and Jewish eras (AM).
In Muslim countries, it is also sometimes denoted as H from its Arabic form (سَنَة هِجْرِيَّة, abbreviated ھ).
In English, years prior to the Hijra are reckoned as BH ("Before the Hijra")