Hijri Islamic calendar converter for WEB (Hijri) calendar to the Gregorian or vice versa by the Gregorian calendar in the Islamic world. The Islamic calendar is lunar; the division of the months of the year is determined by the phases of the moon. The Islamic year is called 'Hijri' and contains 12 months. The year of immigration of the Prophet Muhammad from Mecca to Medina; which falls on 622 AD; is regarded as the first year for Muslims. Screenshot; 2012