# The Encyclopedia Americana (1920)/Hegira

**HEGIRA**, hĕj'ĭ-ra, **HEJRA**, or **HIJRA**,
an Arabic word meaning “going away,”
commonly used to indicate Mohammed's flight from
Mecca, in 622 A.D. In 639 Caliph Omar instituted
a new Moslem calendar to begin with the
first day of the first month of the year in which
the flight took place. The Mohammedan year,
as a lunar year, is shorter than ours by ten days,
21 hours and 14-2/5 seconds. A rough and ready
method for finding the year in our calendar
corresponding to a given year in the Mohammedan
is to subtract from the latter 1/33 of itself
and add 622 to the remainder. To find the
precise year and day multiply the year of the
Hegira by 970,224, strike off from the product
six decimal figures and add 621.5774; this will
give the year of the Christian era; and the day
of the year is got by multiplying the decimal
figures by 365.