The Islamic Calendar's Year One Began on July 16, 622
On this day · 16 July 622
When Muslim scholars later set a calendar, they backdated its very first day to a Friday in midsummer 622.
The Islamic calendar counts its years from the Hijrah — the migration of the Prophet Muhammad and his followers from Mecca to Medina. By long-standing reckoning, its first day, 1 Muharram in the year 1 AH (Anno Hegirae), falls on Friday, 16 July 622 CE by the Julian calendar.
That starting point was chosen retrospectively. The calendar itself was not fixed at the moment of the migration but established years afterward, and scholars then anchored year one to the beginning of the Arabian lunar year in which the Hijrah occurred. The U.S. Naval Observatory still uses this 16 July 622 epoch as the official zero point for converting modern dates into Hijri years.
The count begins not with a battle or a birth, but with a journey.
Because the calendar is purely lunar — twelve months of roughly 29 or 30 days — its year runs about 11 days shorter than the solar year, so Islamic dates drift steadily backward through the seasons.
Sources & references
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