The Hijri year or era is the era used in the Islamic lunar calendar, beginning its count from 622 , the year of the migration of Muhammad and his followers from Mecca to Yathrib (later Medina), an event known as the Hijra. It is denoted in Arabic with a hāʾ , the first letter of Hijra. It is denoted in English by the abbreviation AH, which follows the format of the Dionysian era in representing a Latin phrase. means "in the year of the Hijra" and should technically precede dates in the manner of . More commonly, it is placed after the year.