Conversions may be done online (see list of programmes at the bottom of this page), using the Tabular Islamic calendar (see section above) or, most accurately, through the Jewish calendar, which is accurate to one day in 15,186 years. Theoretically, the days of the months correspond in both calendars if the displacements which are a feature of the Jewish system are ignored. The table below gives, for nineteen years, the Muslim month which corresponds to the first Jewish month.
This table may be extended since every nineteen years the Muslim month number increases by seven. When it goes above twelve, subtract twelve and add one to the year AH. From AD412 to AD632 inclusive the month number is 1 and the calculation gives the month correct to a month or so. AD622 corresponds to BH1 and AH1. For earlier years, year BH = (623 or 622) - year AD).
An example calculation: What is the civil date and year AH of the first day of the first month in the year AD20875?
We first find the Muslim month number corresponding to the first month of the Jewish year which begins in AD20874. Dividing 20874 by 19 gives quotient 1098 and remainder 12. Dividing 2026 by 19 gives quotient 106 and remainder 12. The two years are therefore (1098-106)=992x19 years apart. The Muslim month number corresponding to the first Jewish month is therefore (992x7)=6944 higher than in 2026. To convert into years and months divide by twelve - 6944/12=578 years and 8 months. Adding, we get 1447y 10m + 20874y - 2026y + 578y 8m = 20874y 6m. Therefore, the first month of the Jewish year beginning in AD20874 corresponds to the sixth month of the Muslim year AH20874. The worked example in Hebrew calendar#Conversion between Jewish and civil dates shows that the civil date of the first day of this month (ignoring the displacements) is Friday, 14 June. The year AH20875 will therefore begin seven months later, on the first day of the eighth Jewish month, which the worked example shows to be 7 January, AD20875 (again ignoring the displacements). The date given by this method, being calculated, may differ by a day from the actual date, which is determined by observation.
A reading of the section which follows will show that the year AH20875 is wholly contained within the year AD20875, also that in the Gregorian calendar this correspondence will occur one year earlier. The reason for the discrepancy is that the Gregorian year (like the Julian) is slightly too long, so the Gregorian date for a given AH date will be earlier and the Muslim calendar catches up sooner.
[edit] Current correlationsAn Islamic year will be entirely within a Gregorian year of the same number in the year 20874, after which year the number of the Islamic year will always be greater than the number of the concurrent civil year. The Islamic calendar year of 1429 occurred entirely within the civil calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 civil years). More are listed here:
Islamic year within civil year
Because a hijri or Islamic lunar year is between 10 and 12 days shorter than a civil year, it begins 10–12 days earlier in the civil year following the civil year in which the previous hijri year began. Once every 33 or 34 hijri years, or once every 32 or 33 civil years, the beginning of a hijri year (1 Muharram) coincides with one of the first ten days of January. Subsequent hijri New Years move backward through the civil year back to the beginning of January again, passing through each civil month from December to January.
[edit] UsesThe Islamic calendar is now used primarily for religious purposes, and for official dating of public events and documents in Muslim countries. Because of its nature as a purely lunar calendar, it cannot be used for agricultural purposes and historically Islamic communities have used other calendars for this purpose: the Egyptian calendar was formerly widespread in Islamic countries, and the Iranian calendar and the 1789 Ottoman calendar (a modified Julian calendar) were also used for agriculture in their countries. In Morocco, the Berber calendar (another Julian calendar) is still used by farmers in the countryside. These local solar calendars have receded in importance with the near-universal adoption of the Gregorian calendar for civil purposes. As noted above, Saudi Arabia uses the Islamic calendar to date religious occasions such as Ramadan, Hajj, etc. and the Umm-al-Qura calendar, based on calculations, for administrative purposes and daily government business.[47] In Indonesia, the Javanese calendar, created by Sultan Agung in 1633, combines elements of the Islamic and pre-Islamic Saka calendars.
British author Nicholas Hagger writes that after seizing control of Libya, Muammar Gaddafi "declared" on 1 December 1978 "that the Muslim calendar should start with the death of the prophet Mohammed in 632 rather than the hijra (Mohammed's 'emigration' from Mecca to Medina) in 622". This put the country ten solar years behind the standard Muslim calendar.[48] However, according to the Encyclopedia of the Developing World in 2006, "More confusing still is Qaddafi's unique Libyan calendar, which counts the years from the Prophet's birth, or sometimes from his death. The months July and August, named after Julius and Augustus Caesar, are now Nasser and Hannibal respectively."[49] Reflecting on a 2001 visit to the country, American reporter Neil MacFarquhar observed, "Life in Libya was so unpredictable that people weren't even sure what year it was. The year of my visit was officially 1369. But just two years earlier Libyans had been living through 1429. No one could quite name for me the day the count changed, especially since both remained in play. ... Event organizers threw up their hands and put the Western year in parentheses somewhere in their announcements."[50]