Hijra (هِجْرَة), or withdrawal, is the word that is used for the movement of Muhammad and most of his followers from Mecca to Medina in 622. The Hijra marks the beginning of the Islamic calendar. Alternate spellings of this Arabic word in the Latin alphabet are Hijrah, or Hegira in Latin. 
Chronology of the HijraEdit
- Day 1: Thursday 26 Safar AH 1, 9 September 622
- Left home in Mecca. Stayed three days in the Cave of Thawr near Mecca.
- Day 5: Monday 1 Rabi' I AH 1, 13 September 622
- Left the environs of Mecca. Traveled to the region of Yathrib.
- Day 12: Monday 8 Rabi' I AH 1, 20 September 622
- Arrived at Quba' near Medina.
- Day 16: Friday 12 Rabi' I AH 1, 24 September 622
- First visit to Medina for Friday prayers.
- Day 26: Monday 22 Rabi' I AH 1, 4 October 622
- Moved from Quba' to Medina.
The Muslim dates are in the Islamic calendar extended back in time. The Western dates are in the Julian calendar. The Hijra is celebrated annually on 8 Rabi' I, about 66 days after 1 Muharram, the first day of the Muslim year. Many writers confuse the first day of the year of the Hijra with the Hijra itself, erroneously stating that the Hijra occurred on 1 Muharram AH 1 or 16 July 622.
- To be precise, the first Hijra was in 615 when a band of Muslims were counseled by Muhammad to escape persecution in Mecca and travel to the Kingdom of Axum, which was ruled by a Christian king (see Islam in Ethiopia). Muhammad himself did not join this emigration. In that year, his followers fled Mecca's leading tribe, the Quraysh, who sent emissaries to Axum to bring them back to Arabia. The nascent movement faced growing opposition and persecution. When Muhammad and his followers received an invitation from the people of Yathrib, they decided to leave Mecca.
- All dates given above may have occurred about 89 days (three lunar months) earlier. The Muslim dates may be those recorded in the original Arabic calendar and their month names may not have been changed to account for the (probably three) intercalary months inserted during the next nine years until intercalary months were prohibited during the year of Muhammad's last Hajj (AH 10).
- F. A. Shamsi, "The Date of Hijrah", Islamic Studies 23 (1984): 189-224, 289-323.