Hegira
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
The epoch or account of time used by the Arabians and the Turks, who begin their computation from the day that Mahomet was compelled to escape from Mecca, which happened on Friday, July 16, A. D. 622, under the reign of the Emperor Heraclius.
Wharton.