HEJIRA or HEGIRA, the name of the Mohammedan era (Arab, hijra, flight). It dates from 622, the year in which Moham med "fled" from Mecca to Medina to escape the persecution of his kinsmen of the Koreish tribe. The years of this era are dis tinguished by the initials "A.H." (anno hegirae). The Mohamme dan year is a lunar one, about I I days shorter than the Christian. Although Mohammed himself appears to have dated events by his flight, it was not till later that the actual era was systematized by Omar, the second caliph (see CALIPHATE), as beginning from the first day of Muharram (the first lunar month of the year) which in that year (639) corresponded to July 16. The term hejira is also applied in its more general sense to other "emigra tions" of the faithful, e.g., to that to Abyssinia (see MOHAMMED), and to that of Mohammed's followers to Medina before the cap ture of Mecca. These latter are known as Mulia jirun.