Also known as hijrah calendar. Lunar calendar consisting of twelve months, each of which lasts from the first sighting of one crescent moon to the first sighting of the next, approximately twenty-nine or thirty days. The year is 354 days long. The months in order are Muharram, Safar, Rabi al-Awwal, Rabi al-Thani, Jumada al-Ula, Jumada al-Akhirah, Rajab, Shaban, Ramadan, Shawwal, Dhu al-Qadah, and Dhu al-Hijjah. Holidays occur during different seasons from year to year since the calendar is lunar rather than solar. Days run from sunset to sunset. Year 1 of the Islamic calendar begins with the Muslim emigration (hijrah) from Mecca to Medina in 622 C.E.