Islamic calendar
The Islamic calendar, known as the Hijri calendar, counts twelve lunar months in a year of 354 or 355 days. That is about eleven days shorter than a solar year, so each month arrives roughly eleven days earlier against the equinoxes every year. The Astronomical Almanac notes that the cycle of twelve lunar months regresses through the seasons over about 33 solar years. Ramadan, the month of fasting, therefore wanders through summer heat and winter cold across a single lifetime. Most Muslim-majority countries run civil life on the Gregorian calendar. They keep the Hijri one for holidays, the annual fast and the season of the great pilgrimage. This documentary asks how a calendar that ignores the seasons came to be counted. It asks why year one was chosen as it was, and who gets to declare that a month has begun. It also asks why neighboring countries can disagree about the very same night.
Rajab, Dhu'l-Qa'da, Dhu'l-Hijja and Muharram were the months when fighting stopped. Islamic tradition is unanimous that the Arabs of Tihamah, Hejaz and Najd split the year into permitted months and forbidden ones. Rajab stood alone, while the other three gathered around the pilgrimage season.
Procopius, an outside witness, describes a similar custom. He writes of an armistice that the Eastern Arabs of the Lakhmid al-Mundhir respected for two months around the summer solstice of 541 CE. Muslim historians, however, do not tie the forbidden months to any particular season.
The Qur'an links the four months to a word, Nasi, which literally means postponement. Muslim tradition says the decision to postpone was administered by the tribe of Kinanah. It was carried out by a man known as al-Qalammas of Kinanah and, after him, his descendants. Scholars still argue about what the postponement actually did.
One camp holds that the pre-Islamic calendar of central Arabia was purely lunar, much like the modern one. On this reading, the Meccan Arabs only shifted which months counted as forbidden within a given year. Ibn Hisham and Ibn Manzur support this view, as does the large body of Qur'anic commentary. An early Sabaic inscription records a religious ritual that was postponed because of war, and its verb has nothing to do with adding months. A standard reference on Islam concludes that the system was meant to move the Hajj and its fairs near Mecca into a suitable season, not to build a fixed calendar.
The other camp agrees the calendar began as lunar. It argues that around 200 years before the Hijra, the Arabs turned it into a lunisolar calendar. An extra month was added from time to time, to keep the pilgrimage in the season when merchandise was most abundant. The medieval astronomer Abu Ma'shar al-Balkhi first proposed this, and al-Biruni and al-Mas'udi later agreed. In one explanation Abu Ma'shar mentions, the Arabs learned the practice from the Jews, whose official called the Nasi decided when their calendar needed an extra month. Some sources say seven months were added over nineteen years. Others say nine months over 24 years, and scholars have reached no consensus.
In the tenth year of the Hijra, Muslims believe, God revealed the prohibition of the Nasi. It is recorded in Surah At-Tawbah, verses 36-37, which state that "the number of months ordained by Allah is twelve", four of them sacred. Muhammad repeated the ban in his farewell sermon, delivered on Mount Arafat on 9 Dhu'l-Hijja AH 10, during the farewell pilgrimage to Mecca. The source gives its Julian date as Friday, the 6th of March 632. He told the crowd, "In the eyes of God the number of the months is twelve." He named the sacred months as Rajab, standing alone, and three consecutive others: Dhu'l-Qa'da, Dhu'l-Hijja and Muharram, which are months 11, 12 and 1.
The question of what Nasi meant matters to historians. If it meant adding months, nobody can say how many were added between AH 1 and AH 10. Western dates for the Hijra, the Battle of Badr, the Battle of Uhud and the Battle of the Trench could then be off by one, two, three or even four lunar months.
The Year of the Elephant gave Arabia one of its most famous year names. According to Islamic tradition, Abraha, governor of Yemen under the Christian Kingdom of Aksum, tried to destroy the Kaaba with an army that included several elephants. The raid failed, and the year became the one in which Muhammad was born, a story told in the surah al-Fil. Most scholars equate it with 570 CE, though a minority prefer 571.
Naming a year after a major event was ordinary custom, and the first ten years of the Hijra followed it. Al-Biruni lists them: the year of permission, the year of the order of fighting, the year of the trial, the year of congratulation on marriage, and the year of the earthquake. The list continues with the year of enquiring, the year of gaining victory, the year of equality and the year of exemption. The tenth is the year of farewell.
Around 638, in 17 AH, Abu Musa al-Ash'ari complained to the caliph Umar. He was an official of Umar's in Basra, and the letters he received carried no year. Without one, he could not tell which instructions were the most recent. Umar, who reigned from 634 to 644, debated the problem with his counsellors. He decided that the first year should be the year Muhammad arrived at Medina, which was called Yathrib before that. Uthman then suggested that the months begin with Muharram, in line with the established custom of the Arabs.
The choice left a small oddity. The emigration itself took place in Safar and Rabi' I, two months before the Muharram that opens the new fixed calendar. The calendar takes its name from the Hijra, the move in 622 CE by which Muhammad and his followers left Mecca for Medina and founded the first Muslim community, the ummah.
Medieval Muslim astronomers worked out that 1 Muharram AH 1 fell on Friday, the 16th of July 622, in the Julian calendar. They found the date by projecting their own tabular calendar backward, with alternating 30- and 29-day months and eleven leap days every 30 years. Al-Biruni cited the same date in the year 1000 CE. That Islamic day began at sunset on the evening of the 15th of July. A thin crescent moon would first have become visible then, about a day and a half after the astronomical new moon on the morning of the 14th.
F A Shamsi argued in 1984 that the Arabic calendar was never intercalated at all. In his account, the day Muhammad moved from Quba' to Medina was originally 26 Rabi' I, and 1 Muharram AH 1 matched what people had been observing. The paper trail is thin. Michael Cook and Patricia Crone, in their book Hagarism, cite a coin from AH 17. The earliest surviving Hijri date set beside a date from another calendar, the Coptic, appears on an Egyptian papyrus from AH 22, catalogued as PERF 558.
The hilal, the thin crescent of a new moon, decides when a month begins. Traditionally, the first day of each month is the day that starts at the sunset after the first sighting. If the crescent is not seen after the 29th day, because clouds block the view or the western sky is still too bright when the moon sets, the day beginning at that sunset is the 30th. Months therefore run 29 or 30 days, usually in no discernible order.
The sighting must be made by one or more trustworthy men testifying before a committee of Muslim leaders. Working out the most likely day for a sighting gave Muslims a motive to study astronomy. That motive kept Islam at the forefront of the science for many centuries.
A purely astronomical lunar calendar behaves differently. It alternates months of 30 and 29 days by convention, because the moon's average revolution takes 29.53 days. That leaves a drift of 44 minutes per month, which adds up to one full day in 2.73 years. The sighting-based calendar never strays more than three days from this astronomical one.
Geography complicates every announcement. The crescent becomes visible only about 17 hours after conjunction, the moment the moon sits most directly between Earth and Sun. Weather, time and position all have to cooperate. The moon sets progressively later than the sun as one travels west, so Western Muslim countries may see the new moon a day earlier than eastern ones. Each state observes the moon for itself, or waits for 30 days to finish. Month starts can therefore differ between countries within the 48 hours after conjunction.
Saudi Arabia still uses the sighting method. Since AH 1419, which began in 1998, the government has set up several official hilal committees. The religious authorities also accept testimony from less experienced observers. They often announce a sighting on a date when none of the official committees could see the crescent.
Other states try rules tied to astronomy. Malaysia, Indonesia and a few others start each month at sunset on the first day the moon sets after the sun. Egypt requires the moon to set at least five minutes after the sun. A detailed analysis of the available data finds major discrepancies between what countries say they do and what they actually do. In some instances, what a country says it does is impossible. In any one country, the calendar's information does not extend beyond the current month.
If the calendar were built entirely from astronomical calculation, Muslims everywhere could use it the way the world uses the Gregorian calendar. Whether that is permitted is disputed. A majority of theologians oppose calculation beyond the rule that a month lasts no fewer than 29 and no more than 30 days. They point to Muhammad's recommendation to observe the new moon of Ramadan and Shawal when fixing the start of those months.
Some jurists see no contradiction between that teaching and calculation. They consider the recommendation adapted to the culture of its time, and not an act of worship. Ahmad Muhammad Shakir endorsed calculating all months in 1939, and Yusuf al-Qaradawi did so in 2004. The Fiqh Council of North America followed in 2006, and the European Council for Fatwa and Research in 2007.
France shows how hard it is to put the idea into practice. In 2012, the major Muslim associations of France announced a calendar based on astronomical calculations. It took into account whether a crescent could be sighted anywhere on Earth. The French Council of the Muslim Faith formally adopted the rule in 2013. Then, on the eve of Ramadan 2013, the council's new leadership chose to follow the Saudi announcement instead of the rule it had just adopted. The Muslim community of France divided, with some members following the new rule and others following Saudi Arabia.
Turkey's Presidency of Religious Affairs, the Diyanet, calculates the Turkish Islamic calendar several years in advance. From 1 Muharrem 1400 AH, the 21st of November 1979, until 29 Zilhicce 1435, the 24th of October 2014, a month began on an evening when a strict rule was met. Somewhere on the globe, the computed centre of the crescent at local sunset had to sit more than 5 degrees above the horizon and more than 8 degrees from the Sun. Under the current rule, the computed crescent has to be above the horizon of Ankara at sunset.
Saudi Arabia's Umm al-Qura calendar has changed its parameters repeatedly. Before AH 1420, which began on the 18th of April 1999, a month started if the moon was at least 12 hours old at sunset in Riyadh. This often led the Saudis to celebrate holy days one or even two days before other predominantly Muslim countries. That included the dates of the Hajj, which can only be dated using Saudi dates because it is performed in Mecca.
From AH 1420 to 1422, the rule changed to moonset after sunset at Mecca. That is essentially the rule Malaysia and Indonesia use, apart from where the observer stands. Since the beginning of AH 1423, on the 16th of March 2002, the geocentric conjunction must also occur before sunset. This ensures the moon has moved past the sun, even if the sky is too bright to see the crescent.
In 2007, the Islamic Society of North America, the Fiqh Council of North America and the European Council for Fatwa and Research announced they would use the same parameters. They wanted to fix the start of every lunar month, and every religious observance, well in advance. They called this a first step toward unifying Muslims' calendars around the world. Then, on the 14th of February 2016, Saudi Arabia adopted the Gregorian calendar for paying government salaries, as a cost-cutting measure. It kept the Islamic calendar for religious purposes.
The tabular Islamic calendar skips both sight and astronomy and works out months by arithmetic. It runs on a 30-year cycle with 11 leap years of 355 days and 19 years of 354 days. Over the long term it is accurate to one day in about 2,500 solar years, though it can stray a day or two in the short term. The Isma'ili-Taiyebi Bohras, who have the institution of da'i al-mutlaq, follow a tabular calendar prepared on astronomical calculations from the days of the Fatimid imams.
Microsoft uses the "Kuwaiti algorithm" to convert Gregorian dates into Islamic ones. The company claimed it rests on a statistical analysis of historical data from Kuwait. In fact it matches a known tabular calendar.
Safar, the second month, means void. The name supposedly comes from pre-Islamic Arab houses standing empty at that time of year, while their occupants gathered food. Rabi' al-Awwal, "the first spring", also relates to grazing, because cattle were grazed in that month. It is a month of celebration for many Muslims, since Muhammad was born in it.
Jumada, the parched-land months, are often considered the pre-Islamic summer. The name may also relate to a verb meaning "to freeze", and one account says water froze at this time of year. Rajab means respect or honour, and may relate to a verb meaning "to remove". Pre-Islamic Arabs supposedly removed the heads of their spears and refrained from fighting.
Sha'ban means scattered, from the time when Arab tribes dispersed to find water. Another account says it lies between Rajab and Ramadan. Ramadan means burning heat, a name linked to high temperatures and to the burning of worldly desire on an empty stomach. Muslims fast and avoid sin from pre-dawn until sunset, and they should give charity to the poor and needy. Shawwal means raised, because female camels, normally in calf at that time, would raise their tails. Its first day brings Eid al-Fitr, the Festival of Breaking the Fast.
Dhu'l-Hijja is the month of pilgrimage, when pilgrims from around the world gather at Mecca to visit the Kaaba. The Day of Arafah falls on the ninth, and Eid al-Adha, the Festival of the Sacrifice, begins on the tenth and ends on the thirteenth.
Some communities once used entirely different month names. Two naming systems called the Afghan lunar calendar were used by the Pashtuns and by the Hazaras. They lasted until the reign of Amanullah Khan, when the Solar Hijri calendar was formalized across Afghanistan. In Xinjiang, the Uyghur Muslims used the Turki lunar calendar, with its own month names, until the Gregorian calendar was adopted in the 20th century.
The calendar's feast days show where traditions differ. The 10th of Muharram is Ashura. Shias and Sunnis alike mark the martyrdom of Husayn ibn Ali, Muhammad's grandson, and his followers. Sunnis also remember Moses crossing the Red Sea on that day. Sunnis celebrate Mawlid, the birth of the Prophet, on 12 Rabi al-Awwal, while Shias celebrate it on the 17th. The majority of Muslims mark Isra and Mi'raj on 27 Rajab, and 15 Sha'ban is the Night of Forgiveness. Revelation of the Qur'an is remembered on 27 Ramadan, though Indonesia and Malaysia use the 17th. Shia Muslims also observe the 13th of Rajab as the birthday of Ali ibn Abi Talib and the 21st of Ramadan as his martyrdom.
Twelver Shia Muslims even place the new year elsewhere. They hold that the first month is Rabi' al-Awwal, not Muharram, because the Hijrah took place in that month. This changes how years are assigned to events. The Battle of Karbala, fought in Muharram, took place in 60 AH according to Shias and in 61 AH according to Sunnis.
The Islamic day begins at sunset and ends at the next sunset, so each day starts at nightfall. Five of the seven weekdays are named by their order, from al-Ahad, "the One", to al-Khamis, "the Fifth". The sixth is al-Jumah, "the Gathering", and the seventh is as-Sabt, "the Rest".
On Friday, Muslims gather at a local mosque at noon for the Friday prayer. Countries have answered in different ways. Egypt and Saudi Arabia make Friday and Saturday the weekend. Other countries choose Thursday and Friday, and Iran keeps Friday alone as a day of rest. Indonesia, Turkey, Pakistan, Morocco, Nigeria and Malaysia have a Saturday-Sunday weekend, with a Friday working day that includes a long midday break for worship.
Because it is purely lunar, the Hijri calendar cannot guide farmers. Islamic communities have historically used other calendars for agriculture, including the Egyptian calendar, the Iranian calendar, Akbar's calendar and the 1789 Ottoman calendar, a modified Julian one. Akbar's calendar is the source of the Bengali calendar. In the Levant and Iraq, the Aramaic month names of the Babylonian calendar still serve for secular matters. Berber farmers in the Maghreb countryside still use the Julian calendar for agrarian purposes. In Indonesia, the Javanese calendar blends the Islamic calendar with the pre-Islamic Saka calendar. Iran counts its Solar Hijri years from the same migration of 622 CE.
Libya produced the strangest variation. British author Nicholas Hagger writes that after seizing control of Libya, Muammar Gaddafi declared on the 1st of December 1978 that the Muslim calendar should start with the Prophet's death in 632. That put the country ten solar years behind the standard count. A 2006 reference work adds that July and August, named after Julius and Augustus Caesar, became Nasser and Hannibal. American reporter Neil MacFarquhar visited in 2001 and recalled, "Life in Libya was so unpredictable that people weren't even sure what year it was." He found his year officially 1369, though two years earlier Libyans had lived through 1429. Event organizers put the Western year in parentheses.
Software has had to learn the calendar too. Hijri support was available in later versions of traditional Visual Basic, and it is also available in the .NET Framework. Since the release of Java 8, the Islamic calendar has been supported in the new Date and Time API. Meanwhile the count goes on. In Gregorian terms, 1447 AH runs from the 26th of June 2025 to approximately the 15th of June 2026.
Updated
Common questions
What is the Islamic calendar and how long is its year?
The Islamic calendar, also called the Hijri calendar, is a lunar calendar of 12 lunar months in a year of 354 or 355 days. It sets the dates of Islamic holidays and rituals, such as the annual fast and the season of the great pilgrimage.
When does the Islamic calendar start counting years?
The Islamic calendar counts from the Hijrah, the migration of Muhammad and his followers from Mecca to Medina in 622 CE. Medieval Muslim astronomers placed 1 Muharram AH 1 on Friday, the 16th of July 622, in the Julian calendar.
Who introduced the Islamic calendar era?
The caliph Umar introduced the Hijri era around 638 CE (17 AH), after Abu Musa al-Ash'ari complained that his letters carried no year. Umar chose the year of Muhammad's arrival at Medina as year one, and Uthman suggested starting the months with Muharram.
How is the start of a month decided in the Islamic calendar?
Traditionally, a month starts on the day beginning at the sunset after the first sighting of the hilal, the crescent moon. If the crescent is not seen after the 29th day, the next day is the 30th, so months last 29 or 30 days.
Why do Islamic calendar months move through the seasons?
The average lunar year is 10.87513 days shorter than the average solar year, so Hijri months advance about eleven days earlier each year relative to the equinoxes. The cycle of twelve lunar months regresses through the seasons over about 33 solar years.
Which are the four sacred months of the Islamic calendar?
The four sacred months are Rajab (month 7) and the three consecutive months Dhu'l-Qa'da (11), Dhu'l-Hijja (12) and Muharram (1). Fighting is forbidden in these months, and the same four were forbidden in the pre-Islamic Meccan calendar.
What is the difference between the Islamic calendar and the Umm al-Qura calendar?
The traditional Islamic calendar relies on sighting the crescent, while the Umm al-Qura calendar is based on astronomical calculations. Since AH 1423, which began on the 16th of March 2002, the Umm al-Qura rule requires conjunction before sunset and moonset after sunset at Mecca.
Which countries use the Islamic calendar for civil purposes?
In almost all countries where Islam is the predominant religion, the civil calendar is the Gregorian calendar, and the Hijri calendar is the religious one. Saudi Arabia kept the Islamic calendar for religious purposes when it adopted the Gregorian calendar for government salaries on the 14th of February 2016.
All sources
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