The New International Encyclopædia/Hejira
HEJIRA, hĕjĭ-rȧ (Ar. hyra, flight, from hajara, to abandon). The flight of Mohammed from Mecca to Medina to escape the persecution of his kinsmen, the Koreish (see Mohammed), and the starting-point of the Mohammedan Era. The exact day of the flight is uncertain. The custom of dating events with reference to it originated with Mohammed himself, but the calendar was first instituted by Omar, seventeen years after the event, and was made to begin, not with the day of the flight, but with the first day of the year (i.e. the first of the month Muharram) in which it took place, which corresponds with July 16, 622, of the Christian Era. The Mohammedan year is a lunar year, of 354 days, 9 hours, hence about 11 days shorter than the Christian year, and this fact must be borne in mind in computing the date of the Christian calendar corresponding to any given Mohammedan date. An easy rule, which will give the year approximately, is to deduct three per cent. from the Mohammedan year and add the result to 622. Thus the year of the Hejira 1321 will be found to correspond roughly to the year 1903 of the Christian Era (1321 — 40 + 622 = 1903). For more accurate results, consult Wüstenfeld, Vergleichungstabellen der mohammedanischen und christlichen Zeitrechnung, continued by Mahler (Leipzig, 1854-87).