The Moslem calendar is different from our Gregorian one. For a start the years are lunar-based and therefore 10 or 11 days shorter than our (solar-based) Western system. Then, where we count back to the year of the birth of Christ, the Moslem year one is predicated on the Hegira (Mohammed’s flight from Mecca to Medina).
Thus in 1978 the current Islamic year was 1398.
Actually I remember reading somewhere that modern science has demonstrated that our (Julian) calendar, established during the reign of Pope Gregory in the 6th century, was computed erroneously (by six years) and that Jesus Christ was born in 6 B.C, or in other words, He was born six years before He was born.
(This makes nonsense, by the way, of the well-meaning literalists who attempt to impugn significance in the dispersion of the various astrological bodies in the night skies eg. the twinkle twinkle little star that three wise men were following).
The lunar month has 29 and a half days and thus Moslem months are not tied to the seasons as in our calendar. Religious days and holidays are rotative and therefore have no fixed date; (only our Easter is a moveable feast, being based on lunar calculations).
Days begin at sunset rather than at midnight – the night of a day therefore precedes the day rather than following it, i.e. Monday night is the evening before Monday.
Some Algerian calendars were printed with both the Gregorian and the Islamic dates. They were read from right to left. While the Gregorian calendar had been officially adopted, the Islamic one was still used and dictated the holy days (or holidays).
Meanwhile my guitar gently weeps