The Lunar Hijri calendar

Fact sheet

Scientific classification

• Lunar: its unit is the lunar month (conjunction to conjunction, 29.53059 days on average), and its year is twelve months unrelated to the solar year. It is the most widely used purely lunar calendar today.
• Observational in origin: the month begins with the sighting of the crescent after sunset, so its first day is not known for certain until that evening; many countries have moved to astronomical criteria computed in advance. Reingold and Dershowitz treat it in two forms: “arithmetical” (tabular) and “observational.”
• An arithmetical (tabular) form: devised by Muslim astronomers: months alternating 30 and 29 days, and 11 leap years of 355 days in every 30 years. Its error against the mean lunar month is a day in about 2,500 years, but it can differ from sighting by one or two days.
• Its relation to the seasons: it does not try to stay in the seasons; it separates from the solar year by about 10.9 days a year, and a month returns to its season after about 33 lunar years (32 solar years).

Rules

1. The month: begins when the crescent is established on the evening of the 29th; if it is not, the month is completed to thirty days. In the hadith: “Fast when you see it and break the fast when you see it; if it is obscured from you, complete the count as thirty.”
2. The day: begins at sunset, so the night of the first of the month precedes its day — the tarawih prayers of the first of Ramadan, for example, are prayed on it.
3. The year: twelve months with no addition: “Indeed, the number of months with God is twelve months” [At-Tawbah: 36]. So it is 354 or 355 days long, and may become 353 or 356 under sighting when several short or full months come in a row.
4. Differing horizons: some jurists hold that each country has its own sighting, others that a sighting in one country binds all; hence the first of the month differs between countries.

Months and their names

The current names are old Arabic names that predate Islam, most of them taken from the conditions of the time in which they were set. Lisan al-Arab quotes Ibn Durayd: “When they carried the month names over from the old language, they named them after the times in which they fell,” and says of the two Rabi’s: “They were so named because they were fixed at this time, and kept the name at other times.” Their meanings as given in Lisan al-Arab:

The sacred months are four: three consecutive (Dhu al-Qada, Dhu al-Hijja and Muharram) and one apart (Rajab). Al-Biruni and al-Mas‘udi recorded older names for the months, with variant readings, among them “al-Mu’tamir” for Muharram, “Najir” for Safar, “al-Asamm” for Rajab, “Natiq” for Ramadan and “Burak” for Dhu al-Hijja.

Counting the years

• From the year of the Hijra: year 1 is the year in which the Prophet ﷺ migrated to Medina; it begins with the Muharram before it, the Hijra itself being in Rabi al-Awwal.
• The epoch: 1 Muharram 1 AH = Friday 16 July 622 (Julian) in the “civil” tabular reckoning, or Thursday 15 July in its “astronomical” form.
• Matching the years: because the lunar year is shorter, the Hijri count gains a year about every 32–33 Gregorian years. Year 1447 AH began in June 2025, and 1448 AH in June 2026.
• Before the Hijra: some historians write “BH” (before the Hijra) for earlier years, with no year zero.

Methods of starting the month today

• Local sighting: the month is announced after the crescent is sighted in the country itself or nearby, as in Morocco, Pakistan, Oman and others.
• Sighting with calculation as a veto: a sighting is accepted unless calculation shows it to be impossible. This is in essence the resolution of the International Islamic Fiqh Academy (Amman, 1986): sighting is the basis, aided by calculation and observatories.
• The Umm al-Qura calendar (Saudi Arabia): a computed calendar for civil affairs, while religious occasions are announced by the Supreme Court after sighting. Its rule has changed several times: before 1420 AH the month began if the moon’s age at sunset in Riyadh was at least 12 hours; from 1420 AH it began if the moon set after the sun in Mecca; from 1423 AH (2002) the condition that conjunction occur before sunset was added.
• Astronomical possibility criteria: the Istanbul conference (1978) adopted a crescent altitude of 5° and elongation of 8° at sunset, which Turkey’s Presidency of Religious Affairs applied from 1400 AH (1979). Then the “International Hijri Calendar Unity Congress” in Istanbul (2016) approved a unified global calendar on the same criterion, if met anywhere on earth under detailed conditions.
• The new MABIMS criterion (2021): for the countries of South-East Asia (Indonesia, Malaysia, Brunei and Singapore): crescent altitude 3° and elongation 6.4°.
• Advance calculation in the West: the Fiqh Council of North America (2006) and the European Council for Fatwa (2007) adopted calculation to announce the months in advance.
• Tabular: not used for worship; historians and software use it for approximate date conversion, with a 30-year cycle containing 11 leap years (years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29 in its most common form; some forms use 15 instead of 16).

Month starts in 1447–1448: three methods

The first of each month as a Gregorian date (the date of the daytime): this site’s computation, the published Umm al-Qura calendar, and the tabular calendar (the common form). Differences from Umm al-Qura are in bold:

The site’s computation matched Umm al-Qura in 21 of 24 months and was a day earlier in the other three; the tabular calendar differed from it in 14 months by one or two days. The official announcement of religious occasions in each country may differ from all of these, depending on sighting.

Moving through the seasons

The lunar year is about 10.9 days shorter than the solar year, so each Hijri month moves earlier in the solar year every year and passes through all four seasons in about 33 years. An example from the Umm al-Qura calendar:

History

1. Before Islam

   The Arab months and Al-Nasi

   The Arabs knew the lunar months by their present names, the four sacred months, and “Al-Nasi,” administered by the Banu Fuqaym of Kinana: the first of them al-Qalammas Hudhayfa ibn ‘Abd, and the last Abu Thumama Junada ibn ‘Awf, who announced it in the Hajj season. Its nature is disputed (see “The question of Al-Nasi”).
2. 622 CE

   The Hijra

   The Prophet ﷺ migrated from Mecca to Medina, arriving in Rabi al-Awwal, and the year of the Hijra later became the start of the era.
3. 2 AH

   The fast of Ramadan prescribed

   Worship became tied to the sighting of the crescent: “Fast when you see it and break the fast when you see it,” and “They ask you about the new moons. Say: they are times appointed for people and for the Hajj” [Al-Baqarah: 189].
4. 10 AH

   The Farewell Pilgrimage

   The Prophet ﷺ said in his sermon: “Time has come round to its form on the day God created the heavens and the earth; the year is twelve months, four of them sacred.” In the prevailing view, Al-Nasi was abolished then.
5. 16 or 17 AH

   Umar establishes the era

   Abu Musa al-Ash‘ari wrote to Umar ibn al-Khattab that his letters came undated, so he consulted the Companions: he chose to date from the Hijra (the suggestion is attributed to Ali ibn Abi Talib), and made Muharram the first month of the year (attributed to Uthman ibn Affan).
6. 41 AH

   Al-Hasan hands rule to Muawiya

   The Year of Unity. In the thesis of The Creator's Calendar, this is when intercalation ended and the calendar became purely lunar.
7. 3rd–5th c. AH

   The tabular calendar in the astronomical tables

   Muslim astronomers devised the arithmetical form with the thirty-year cycle for computing dates and observations, and al-Biruni and others used it to correlate calendars.
8. 1840 CE

   The Ottoman Rumi calendar

   In 1256 AH the Ottoman state adopted a Julian solar calendar for financial transactions (the “Rumi” or “Mali”), while the Hijri remained for religion and many official matters.
9. 1926 CE

   Turkey adopts the Gregorian

   The Gregorian became the civil calendar in Turkey, followed by many Muslim countries in the 20th century, while the Hijri remained for worship.
10. 1978 CE

    The Istanbul conference

    The astronomical possibility criterion: altitude 5° and elongation 8°, applied in Turkey from 1400 AH.
11. 1986 CE

    The International Islamic Fiqh Academy

    The Amman resolution: sighting is the basis, aided by calculation and observatories.
12. 1999–2002 CE

    The current Umm al-Qura rule

    The computation moved from the moon’s age in Riyadh to moonset after sunset in Mecca (1420 AH), then the condition of conjunction before sunset was added (1423 AH).
13. 2006–2007 CE

    Calculation in North America and Europe

    The Fiqh Council of North America, then the European Council for Fatwa, adopt advance calculation.
14. 2016 CE

    The unified calendar, and a Saudi shift

    The Istanbul congress approves a unified global Hijri calendar. In the same year the Saudi government adopted the Gregorian calendar for salaries and the fiscal year, while Umm al-Qura remained for other matters.
15. 2021 CE

    The new MABIMS criterion

    Altitude 3° and elongation 6.4° in the countries of South-East Asia.

The question of Al-Nasi and the beginning of the purely lunar calendar

All agree that the Arabs before Islam knew “Al-Nasi,” that the Qur’an mentions it — “Al-Nasi is only an increase in disbelief” [At-Tawbah: 37] — and that the Prophet ﷺ said at the Farewell Pilgrimage: “Time has come round to its form on the day God created the heavens and the earth.” They differ over what Al-Nasi was and when the calendar became purely lunar. There are two views:

1. The prevailing view among historians and jurists

• For most exegetes, Al-Nasi was postponing the sanctity of a sacred month to another month. Al-Biruni and others reported a second view: that it was the intercalation of a month to keep the Hajj in a fixed season, taken by the Arabs from the Jews about two hundred years before Islam.
• Al-Nasi was abolished at the Farewell Pilgrimage (Dhu al-Hijja 10 AH), so the calendar became purely lunar from the year 11 AH.
• Then Umar ibn al-Khattab established the era in 16 or 17 AH, on purely lunar months beginning with Muharram.
• On this view, dates of the Prophet’s era are converted to the Gregorian by the purely lunar Hijri, which is what modern tables do.

2. The thesis of The Creator's Calendar

• Al-Nasi is a thirteenth month intercalated so that the lunar months stay in their seasons, and it is the calendar the Arabs used before the Hijra. What the verse condemns is the pre-Islamic manipulation of postponing the sacred months — “they make it lawful one year and forbidden another year, to adjust to the number of what God has made sacred” — not intercalation itself.
• The Prophet ﷺ continued to date by it in Medina, and it remained in use until al-Hasan ibn Ali handed rule to Muawiya (41 AH). The reason for the change to the purely lunar calendar is unknown, but all the evidence and indications point to intercalation having been abolished in Muawiya’s time. This calendar is “The Creator's Calendar” that the site computes.
• The evidence of weekdays: the narrations state that the Hijra was on Monday 12 Rabi al-Awwal of year 1, Badr on Friday 17 Ramadan of year 2, and the Prophet’s death on Monday 12 Rabi al-Awwal of year 11. These days match The Creator's Calendar, while in the purely lunar Hijri they fall on Thursday, Monday and Saturday. More than seventy events, from the birth of the Prophet ﷺ to the handover of rule to Muawiya, are compared in this way.
• The evidence of the seasons: the narrations describe Tabuk in Rajab 9 AH with “intense heat,” the Trench with “intense cold,” and al-Hudaybiyya with the rain-star of Sirius. These match their seasons in The Creator's Calendar and contradict them in the purely lunar calendar.
• The failure of the events of the Prophet’s era to match the purely lunar Hijri is a logical consequence, because the proponents of the prevailing view themselves acknowledge that Al-Nasi was in force until the end of year 10 AH; converting what came before it with purely lunar months drops the months that were intercalated.

This is the thesis of The Creator's Calendar, and it differs from the view of most historians. We have presented both views with their evidence; the details are on the Evidence of Events page and in the Creator's Calendar converter.

Current use

• Worship: throughout the Muslim world: Ramadan, the two feasts, the Hajj, the Day of Arafa, Ashura and the sacred months, waiting periods and expiations.
• Official calendar: in Saudi Arabia (Umm al-Qura, with the Gregorian for salaries and the fiscal year since 2016), and in other countries alongside the Gregorian in official documents.
• Historiography: all Islamic sources are dated by it, and historians need to convert them to the Gregorian with tables or calculation.

On this site

• The site computes the Lunar Hijri calendar astronomically from NASA data (DE441), with Madinah as its reference, using the same month boundaries as The Creator's Calendar: the month begins the day after the conjunction if it occurs before sunset in Madinah, and two days after if it occurs after it. The difference between the two calendars is in the numbering alone: twelve months with no Al-Nasi.
• The day in the site’s computation begins at dawn, not sunset, so the date shown is the date of the daytime. Its epoch is the start of the astronomical month on 15 July 622 Julian (18 July proleptic Gregorian).
• So the first of a month on the site may differ by a day from Umm al-Qura or the sighting announced in your country, as in the comparison table above.
• Range: from the first Hijri year to about the 25th Hijri century, with no year zero before the Hijra.

Hijri to Gregorian Gregorian to Hijri