The Islamic Calendar
For religious purposes, Muslims mark time according to an Islamic calendar called the Hijrah calendar (abbreviated as A.H. or simply H.). This calendar came into use during the caliphate of Omar in 638 C.E., as an alternative to Christian-based or other calendar systems.
In the Islamic calendar, time is counted from the migration (hijrah) of the early Muslim community from Mecca to Madinah in 622 C.E. This event was considered so momentous in Islamic history that Muslims mark it on the calendar as “year zero.” The subsequent passing of time is then related to that event. For example, the year 2008 C.E. corresponds to the year 1429 h.
The Islamic calendar makes use of the lunar cycles to track time. The beginning of each month is marked by the first sighting of the waxing crescent moon and ends with the sighting of the next month's crescent moon. The 12-month lunar year, then, is approximately 11 days shorter than the solar calendar year. Thus, the Islamic months fall in different seasons over time.
The Islamic year and the solar calendar year do not necessarily correspond to each other, and there has been no interest among Muslims to “fix” the calendar to any other system.
Muslims consider it a blessing that the Islamic months fall in various seasons of the year. The fasting month of Ramadan, therefore, sometimes falls during long summer days and sometimes during shorter winter days. Since Muslims are located in both the northern and southern hemispheres, this assures that everyone participates evenly in the fast throughout their lifetimes.
In the Islamic year, there are 12 months of either 29 or 30 days each. They are:
Within the months, each day is counted as beginning with the setting of the sun. Thus what we call “Monday” would actually be counted from sunset on Sunday evening to sunset on Monday evening.
The Qur'an describes the calendar system as follows: “The number of months in the sight of Allah is twelve (in a year); so ordained by Him the day He created the heavens and the earth. Of them, four are sacred. That is the straight usage.” (Qur'an 9:36).
The “Forbidden Months”
In ancient Arab culture, there were traditionally four months during which the tribes agreed to an amnesty on any ongoing fighting. During the months of Muharram, Rajab, Dhul-Qi'dah, and Dhul-Hijjah, any battles were to be automatically suspended in order to allow for trade and travel in the area. This tradition was upheld in Islam, and these four months are called the “forbidden months.” However, if only one side observes the automatic truce and the other side continues fighting, the party observing the truce is obliged to defend itself.
While the Islamic calendar seems quite straightforward, Muslims disagree on aspects of its use in the modern world. Virtually all Muslims would argue for keeping the basic structure of the Islamic calendar, as it is mentioned in the Qur'an and plays an important role in scheduling religious practice. There are differences in opinion, however, in how one may go about determining the beginning and end of each Islamic month.
Is the Hijrah calendar widely used?
The Hijrah calendar is the official calendar in some Muslim countries, particularly Saudi Arabia. Other countries use the Hijrah calendar only to determine the dates of religious holidays; otherwise, they refer to a Gregorian calendar for civil and business purposes.
Traditionally, the determination of the beginning of each month depends on a visible sighting of each new crescent moon, and some Muslims argue that this is the only way the calendar should be used. Some Muslims prefer to use modern astronomical calculations to determine when such a new moon could possibly be visible to estimate dates in the future with closer accuracy and to filter out inaccurate sightings. While most Muslims still argue for a visible sighting, astronomical estimates are increasingly used to estimate dates for printing on calendars. Having an estimate of when dates may fall is increasingly useful when planning ahead for Islamic holidays.