Islamic calendar

Convert Gregorian or Julian dates to Islamic

Convert Islamic to Gregorian or Julian

The Islamic calendar is the official calendar in Kuwait, Saudi Arabia, Yemen, and some other Middle Eastern countries, and is used privately by Moslems everywhere.


Its era begins with the migration from Mecca to Medina of Mohammed, the Prophet of Islam, an event known as the Hegira. The initials A.H. before a date mean “anno Hegirae” or “after Hegira.” The first day of the year is fixed in the Quran as the first day of the month of Muharram. In a.h. 17 ‘Umar I, the second caliph, established the beginning of the era of the Hegira (1 Muharram a.h. 1) as the date that is 16 July 622 ce in the Julian calendar.  Origin of the era.  (Astronomers, however, use an “astronomical Hegira epoch” that began on 15 July 622 (Julian calendar).)


The years are lunar and consist of 12 lunar months. There is no intercalary period, since the Quran (Sura IX, verses 36–37) sets the calendar year at 12 months. Because the year in the Islamic calendar is shorter than a solar year, the months drift with respect to the seasons, in a cycle 32½ years long.


A new month begins when the ulama first sight the lunar crescent after a new moon. If poor visibility makes it impossible to see the moon, the new month begins 30 days after the last one began. The result is that dates may differ from city to city. In modern times, the practice of sighting the moon is observed most strictly for Ramadan, the month of fasting.

The names of the months and their lengths in the calendar are:

Name of month Number of days
Muharram 30
Safar 29
Rabi'al-Awwal 30
Rabi'ath-Thani 29
Jumada l-Ula 30
Jumada t-Tania 29
Rajab 30
Sha`ban 29
Ramadan 30
Shawwal 29
Dhu 'l-Qa`da 30
Dhu 'l-Hijja 29, but 30 days in years 2, 5, 7, 10,
13, 16, 18, 21, 24, 26, and 29

Day and week

The day begins and ends at sunset, at the instant at which a white thread can no longer be distinguished from a black one. The week has 7 days and begins at sunset on Saturday (Gregorian calendar). The names of the days of the week are numbers. The fifth day, which begins at sunset on Thursday, is the day for congregational prayer, but is not considered a day of rest.

Modern usage

Because local determination of dates can be extremely confusing, for historical and civil purposes a version of the calendar that is not based on local month-by-month observation is widely used. In this calendar, months are alternately 30 and 29 days long, making a 354-day year. Since the synodic month is not a whole number of days (and not 29½ days either), to keep the calendar month in sync with the synodic month leap days must be introduced, just as in the Gregorian calendar leap days are introduced to keep the calendar year in sync with the tropical year. These corrections bring the average length of the month to just 2.9 seconds less than the synodic month. If leap days were not added, the beginnings of months would soon not coincide with the first sighting of the lunar crescent.

Leap days are added with reference to a 30 year cycle. One extra day is added at the end of the last month of the year. Thus a leap year has 355 days.

Convert dates in the Gregorian or Julian calendars to the Islamic calendar

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History of the calendar

An interesting aspect of the Islamic calendar is that it is a rare example of a people changing from a lunisolar to a lunar calendar. As with many herding peoples, the earliest Arab calendars were lunar, but around 400 ce they adopted a lunisolar calendar. The Prophet's calendar reform restored the earlier calendar. Some have speculated that this step may have been taken to weaken the power of those who had control of the calendar, much as the French Republicans tried to use calendar reform to break the power of the Roman Catholic Church. Al-Biruni of Kwarizm (973–c. 1050 ce) wrote:

In pagan times the Arabs dealt with their months as the Moslems do now, and their pilgrimage moved through all the four seasons of the year. Then, however, they decided to fix their pilgrimage at a time when their wares, hides and fruits were ready for market; so they tried to make it immovable, to have it always in the most abundant season. So 200 years before the Hegira they learned intercalation from the Jews and, using the same method the Jews did, added the difference between their year and the solar year to the months of the year, whenever the difference had increased to a month. Then at the end of the pilgrimage ceremonies the Kalammas (the Sheiks of a certain tribe, in charge of this task) would come forward, speak to the people, and intercalate a month by giving the next month the name of the present one. People expressed their approval of the Kalammas' decision by applauding. This procedure they called Nasi, that is, shifting, because every second or third year the beginning of the year was shifted.… They could determine the right time [for Nasi] by the risings and settings of the menazil. Thus it remained up to the flight of the Prophet from Mecca to Medina.

[quoted in Ginzel, page 245]


Tables and directions for converting dates in the Islamic calendar to Gregorian dates are found in

G. S. P. Freeman-Grenville.
The Muslim and Christian Calendars.
Oxford: Oxford University Press, 1963.

The Ottoman Empire used a variety of calendars. Descriptions of these and conversions for them are found in

E. Mahler.
Wustenfeld-Mahlersche Vergeichungs-Tabellen der mohammedanischen und christlichen Zeitrechnung. (3rd ed.)
Wiesbaden, 1961.


Faik Resit Unat.
Hicro Tariheri Milade Tarihe Cevirme Kilavuzu.
Ankara: Turk Tarih kurumu basimlvi, 1959.

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