Britannica
Sources used in this answer
How did the Hijrah become the starting point of the Islamic calendar?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Muhammad
The Prophet's Mosque, showing the green dome built above the tomb of Muhammad, Medina, Saudi Arabia.
The Hijrah—the migration of the Prophet Muhammad from Mecca to Medina in 622 CE to escape persecution—serves as the foundational epoch for the Islamic calendar.
While the event itself occurred in 622 CE, the formal establishment of the Hijrah era was introduced in 639 CE by ‘Umar I, the second caliph. To standardize the dating system, ‘Umar I designated the first year of the era (AH, or anno Hegirae) to begin with the first day of the lunar month of Muharram, which corresponded to July 16, 622, in the Julian calendar. This system allows the Islamic calendar to function as a purely lunar dating system that does not attempt to align with the solar, or seasonal, year.123