Encyclopedia  |   World Factbook  |   World Flags  |   Reference Tables  |   List of Lists     
   Academic Disciplines  |   Historical Timeline  |   Themed Timelines  |   Biographies  |   How-Tos     
Sponsor by The Tattoo Collection
Islamic calendar
Main Page | See live article | Alphabetical index

Islamic calendar

The Islamic calendar is a purely lunar calendar of 12 months and a lunar year of usually 354 days. Each month can be either 29 or 30 days long. Because the lunar year is shorter than the solar year, Muslim holy days cycle backwards in relation to the purely solar Western calendar. This has given rise to a Western misperception. The Islamic lunar calendar is not inaccurate, because it is a pure lunar calendar.

The number of days in each month is not set. Rather, each month begins at sunset on the day of the first sighting of the lunar crescent following a new moon. Traditionally, this requires a sighting by a human observer, which was a motivation for the Islamic interest in astronomy that put Islam in the forefront of that science for many centuries. This practice is still followed in a few parts of the world, like Pakistan and Jordan. In some countries like Malaysia and Indonesia, the process is simplified by beginning each month at sunset on the first day that the moon sets after the sun. In Egypt, the month begins at sunset on the first day that the moon sets at least five minutes after the sun. The official Umm al-Qura calendar of Saudi Arabia has recently changed [1].

Before AH 1420, if the moon's age at sunset in Riyad was at least 12 hours, then the day ending at that sunset was the first day of the month. For AH 1420-22, if moonset occurred after sunset at Mecca, then the day beginning at that sunset was the first day of the month. Since the beginning of AH 1423 (March 16, 2002), if moonset occurs after sunset at Mecca and the geocentric conjunction of the sun and moon occurs before sunset, then the day beginning at that sunset will be the first day of the month. Astronomically, both moonset and sunset occur when the refracted upper limbs of the moon and sun reach the refracted horizon, that is, when their centers are 50 arcminutes below the geometric horizon, the horizon determined by a horizontal plane at sea level at the observer's location. These simplifications allow the calendar to be determined in advance, which it cannot be by the traditional method.

Microsoft uses the "Kuwaiti algorithm" to convert Gregorian dates to the Islamic ones. It is based on statistical analysis of historical data from Kuwait.

There exists a variation of the Islamic calendar known as the Tabular Islamic Calendar in which months are worked out by arithmetic rules rather than by observation or astronomical calculation. It has a 30-year cycle in with 11 years are leap years with 355 days instead of 354 days. In the long term, it is accurate to one day in about 2500 years. It also deviates up to about 1 or 2 days in the short term.

Table of contents
1 Dating of the years
2 Predecessors to the Islamic calendar
3 Forbidding intercalary months
4 Names of the Islamic months
5 The names of the days of the week
6 Sacred months and days
7 Current correlations

Dating of the years

In 638 CE (AH 17), the second Caliph Umar ibn al-Khattab (592-644 CE) began numbering the years of the Islamic calendar. He assigned its first year (AH 1) to the year during which Muhammad emigrated to the city of Medina. The first day of the first month (1 Muharram) of that proleptic Islamic year, that is, after the removal of all intercalary months between the Hijra and Muhammad's prohibition of them about ten years later, corresponded to July 16, 622 CE (the actual emigration took place in September). Thus the calendar is also called the Hijra calendar after this migration. Dates in this calendar are usually abbreviated using AH from the Latin phrase Anno Hegirae, "in the year of the Hijra". Years before the Hijra are denoted BH. As in the common calendar, there is no year zero.

Predecessors to the Islamic calendar

The predecessor to the Islamic calendar was a lunisolar calendar in that it used lunar months but was also kept synchronized with the tropical year (that is, based on the motion of the sun), by the insertion of an additional, "intercalary" month when required. Whether the intercalary month (Nasi) was added in the spring like that of the Hebrew calendar or in autumn is debatable. It is assumed that the intercalary month was added between the twelfth month (the month of the Hajj) and the first month (Muharram) of this pre-Islamic year. The two Rabi' months denote grazing and the modern Meccan rainy season, which would promote the growth of grasses for grazing, occurs during autumn—these imply a pre-Islamic year beginning near the autumnal equinox. But it is likely that the rainy season after which these months are named was different before Muhammad's time. Moreover, Muhammad forbade the intercalary month (released the calendar from the seasons) near the end of his life, which implies a pre-Islamic year beginning near the vernal equinox because that is about when AH 10 or 11 began.

Forbidding intercalary months

In the 9th year after the Hijra or migration to Medina, Muhammad forbade the insertion of the additional months. This is expressed in the 9th chapter and 37th verse of the Quran:

"Verily the transposing (of a prohibited month) is an addition to Unbelief: The Unbelievers are led to wrong thereby: for they make it lawful one year, and forbidden another year, of months forbidden by Allah and make such forbidden ones lawful. The evil of their course seems pleasing to them. But Allah guideth not those who reject Faith."

This prohibition was repeated by Muhammad during his last sermon on Mount Arafat during his farewell pilgrimage to Mecca on 9 Dhu al-Hijja AH 10 (this paragraph is often deleted from the sermon by its modern editors as unimportant):

"O People, the unbelievers indulge in tampering with the calendar in order to make permissible that which Allah forbade, and to forbid that which Allah has made permissible. With Allah the months are twelve in number. Four of them are holy, three of these are successive and one occurs singly between the months of Jumada and Shaban."

The three successive holy months are Dhu al-Qada, Dhu al-Hijja, and Muharram, thus preventing an intercalary month from being placed before Muharram.

This means that the Islamic calendar is always shorter than the Gregorian year by about 11 days, and the days of the calendar are not tied to a specific season of the year. It takes 33.6 Islamic years until a complete traversal of the seasons occurs so that a month will fall again during the same season.

Names of the Islamic months

Of all the months in the Islamic calendar, Ramadan is the most sacred, and all Muslims are required to fast during the daytime.

The Islamic months are named as follows:

  1. Muharram ul Haram (or shortened to Muharram) محرّم
  2. Safar صفر
  3. Rabi`-ul-Awwal (Rabi' I) ربيع الأول
  4. Rabi`-ul-Akhir (or Rabi` al-THaany) (Rabi' II) ربيع الآخر أو ربيع الثاني
  5. Jumaada-ul-Awwal (Jumaada I) جمادى الأول
  6. Jumaada-ul-Akhir (or Jumaada al-THaany) (Jumaada II) جمادى الآخر أو جمادى الثاني
  7. Rajab رجب
  8. Sha'aban شعبان
  9. Ramadhan رمضان
  10. Shawwal شوّال
  11. Dhul Qadah ذو القعدة (or Thw al-Qi`dah)
  12. Dhul Hijja ذو الحجة (or Thw al-Hijjah)

The names of the days of the week

These follow the Jewish and Christian order, beginning with Sunday and ending with Saturday. Thus Friday, the weekly holiday, is not either the first or the last day of the islamic week!

Sacred months and days

The Holy Quran, in the ninth chapter and 36th verse, mentions the calendar (translated into English):

"The number of months with Allah has been twelve months by Allah's ordinance since the day He created the heavens and the earth. Of these four are known as sacred; That is the straight usage, so do not wrong yourselves therein, and fight the Pagans."

These four sacred months are: Muharram, Rajab, Dhul Qadah and Dhul Hijja. It is from this verse that it is commonly believed that fighting during sacred months is a sin.

Extremely important dates in the Islamic (Hijri) year are:

Other important dates specific to certain sects in Islam are:

Current correlations

Portions of the Islamic calendar years 1424 and 1425 occur in the Gregorian calendar year 2004. January 1, 2004 is 8 Dhu al-Qa'da 1424 AH. 1 Muharram 1425 AH is February 22, 2004.

The Islamic calendar year of 1429 occurs entirely within the Gregorian calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 Gregorian years). More are listed here:
Islamic year within Gregorian year
Islamic Gregorian Difference
1228 1813 585
1261 1845 584
1295 1878 583
1329 1911 582
1362 1943 581
1396 1976 580
1429 2008 579
1463 2041 578
1496 2073 577
1530 2106 576
1564 2139 575

For a very rough estimate, multiply the Islamic year number by 0.97 and add 622 to get the Gregorian year number.