The Islamic calendar is based on a lunar year of 12 full lunar cycles or months.
Each month begins with the sighting of the new moon.
There are 29 or 30 days in each of the 12 lunar months.
The lunar year is 354 days in total.
Because it is 11 or 10 days shorter than the solar year, the months move ‘backwards’ through the seasons of spring, summer, autumn and winter.
Every 32.5 years, the Islamic calendar has Passed through all the seasons.
The beginning of the Muslim calendar was the year of the Hijrah, when the Holy Prophet Muhammad [s] migrated from Makkah to Madinah. This happened on July the 26, in the year 622 CE. (Christian Era).
The Hijrah calendar begins on the first of Muharram.
Islamic dates are designated in the west by the use of the abbreviation AH which stands for the Latin ‘Anno Hegirae’, or ‘Year of the Hijrah’.
To roughly convert an Islamic calendar year (AH) into the western equivalent (AD), or vice versa, use one of the following equations: