: It was officially adopted about 17 years later by the second Caliph, Umar ibn al-Khattab.
The Hijri calendar began with the , the migration of the Prophet Muhammad from Makkah to Medina in 622 CE . hijri date
: The suffix "AH" stands for Anno Hegirae (Year of the Hijra). How the Hijri Date is Determined : It was officially adopted about 17 years
Unlike the solar-based Gregorian calendar , the Hijri calendar is strictly lunar, meaning each month begins with the first sighting of the new crescent moon (). the Hijri calendar is strictly lunar
: The starting point of the calendar (1 Muharram 1 AH) corresponds to approximately July 16 or 18, 622 CE .