The journey (emigration) undertaken by the Prophet Muhammad, peace be upon him, in 622 C.E. from Makkah to Madinah to escape the persecution of the Prophet and his followers by the Makkhans. The journey took eight days.
The date of the Hijira marks the Muslim new year and is the date from which the Muslim calendar begins. In the Hijira calendar, the months are lunar months, with each month being the period between the two new moons.

