The Islamic calendar is a lunar calendar of twelve months. The Hijri year is approximately 354 days, moving backwards through the solar seasons every 33 years.
"Indeed, the number of months with Allah is twelve months in the register of Allah.", Surah al-Tawbah 9:36
The Hijri calendar is the lunar calendar used throughout the Muslim world to mark religious observances, festivals, and the dates of historical events. It is composed of twelve lunar months, anchored not in the cycles of the sun but in the phases of the moon. A common year contains 354 days and a leap year 355, in contrast to the roughly 365.25 days of the solar Gregorian calendar.
The twelve months are named in Surah at-Tawbah (9:36), where Allah declares: "Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah from the day He created the heavens and the earth; of these, four are sacred." This verse establishes both the number of months and the special status of four of them, in which fighting was forbidden in pre-Islamic Arabia and which Islam preserved as months of heightened reverence.
Because the lunar year is roughly eleven days shorter than the solar year, Hijri dates shift backwards through the Gregorian seasons by about ten to twelve days each year. Over a cycle of roughly thirty-three years, each Hijri month therefore travels through every Gregorian season. Ramadan, for example, may fall in mid-summer for some generations and in mid-winter for others, distributing the burden of fasting equitably across climates and lifetimes.
The calendar takes its name and its starting point from the Hijra, the migration of the Prophet Muhammad ﷺ and his companion Abu Bakr (ra) from Makkah to Madinah in the year 622 of the Common Era. After thirteen years of preaching in Makkah under increasing persecution, this journey marked the founding of the first Muslim community as a political and social body, with the Prophet ﷺ as both spiritual guide and head of state.
For the early community, the Hijra was not merely a change of geography but a turning point: the moment Islam moved from a persecuted faith into an established way of life. The detailed story of the journey, including the night spent in the Cave of Thawr and the arrival in Madinah, is recounted in the Seerah. It was this event, rather than the Prophet's ﷺ birth or the first revelation, that the companions later chose as the foundation of the calendar.
Although the Hijra had taken place in 622 CE, the calendar itself was not instituted until the caliphate of Umar ibn al-Khattab (ra) in roughly 17 AH (around 639 CE). The trigger was an administrative matter: a letter or financial document arrived dated only by month, and there was no agreed-upon year to which it referred. Umar (ra) recognised that as the Muslim state expanded, a shared system of dating was essential for governance, commerce and record-keeping.
Umar (ra) consulted the senior companions. Several suggestions were considered, including dating from the Prophet's birth, the first revelation, or his passing. It was Ali ibn Abi Talib (ra) who proposed dating from the Hijra, on the reasoning that it was the event in which truth was distinguished from falsehood and the Muslim community took its independent shape. Umar (ra) agreed, and it was further decided that the new year would begin with Muharram, the first of the sacred months, so that the year of the Hijra became year 1 AH.
Allah says in Surah at-Tawbah: "Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah from the day He created the heavens and the earth; of these, four are sacred." (Qur'an 9:36). The Prophet ﷺ confirmed in his Farewell Sermon: "Time has come back to its original state which it had when Allah created the heavens and the earth. The year is twelve months, of which four are sacred, three in succession: Dhul-Qa'dah, Dhul-Hijjah and Muharram, and Rajab of Mudar which is between Jumada and Sha'ban." (Bukhari).
Sacredness here means that fighting in these months was forbidden in pre-Islamic Arabia, and Islam preserved that prohibition. Pilgrims could travel safely to Makkah for Hajj in Dhul-Hijjah and for the lesser pilgrimage in Rajab, and return home through Dhul-Qa'dah and Muharram. The reward of righteous deeds is multiplied in these months, as is the gravity of wrongdoing: "So do not wrong yourselves during them." (Qur'an 9:36).
The four sacred months:
The classical method is rukyah, the physical sighting of the new crescent moon by trustworthy witnesses on the 29th evening of the outgoing month. If the crescent is seen, the new month begins the next day. If clouds or haze prevent sighting, the outgoing month is completed to 30 days and the new month begins on the following day. The Prophet ﷺ said: "Begin the fast when you see it (the crescent) and end the fast when you see it; if it is obscured from you, then complete the count of Sha'ban as thirty." (Bukhari 1909).
Modern astronomical calculation can predict the exact moment of conjunction (when the moon passes between Earth and sun) to the second, but Muslim scholars are divided on whether this constitutes a valid replacement for physical sighting. Saudi Arabia and many Gulf states use a combined approach; Turkey, Indonesia and others rely on calculation. The result is that different countries may begin Ramadan or celebrate Eid one day apart, a reality the global ummah has accepted, with each Muslim following the ruling of the local authority where they live.
Listed in Hijri order with their literal meanings and significant dates.
The first month of the Islamic year and one of the four sacred months. The 10th of Muharram (Ashura) is a day of great significance, the Prophet ﷺ fasted on this day and encouraged fasting it and the day before or after. Fasting on Ashura expiates the sins of the previous year.
Key Dates
The second month of the Hijri year. This month was feared in pre-Islamic Arabia as unlucky, but Islam abolished such beliefs. The Prophet ﷺ said: 'There is no safar (ill omen from Safar).' (Bukhari)
The month of the Prophet's birth ﷺ, according to the most accepted view, he was born on Monday 12 Rabi' al-Awwal in the Year of the Elephant (570 CE). The Prophet ﷺ also passed away in this month in 11 AH.
Key Dates
The fourth month of the Islamic year. No specific major Islamic observances fall in this month.
The fifth month. The name 'Jumada' is thought to derive from the Arabic word for frozen water, as this period historically fell in winter.
The sixth month. The Prophet's ﷺ grandfather Abd al-Muttalib is said to have passed away in this month.
One of the four sacred months (al-Ashhurul-Hurum). Fighting was prohibited during this month in pre-Islamic Arabia. The night journey of al-Isra' and al-Mi'raj (the Prophet's ascent through the heavens) is traditionally observed on the 27th of Rajab, though its exact date is debated by scholars.
Key Dates
The month immediately preceding Ramadan. The Prophet ﷺ would fast frequently in Sha'ban, more than in any other month besides Ramadan. The night of the 15th of Sha'ban (Laylat al-Nusf min Sha'ban) is considered by many scholars to be a night of special virtue, though the hadith evidence is debated.
Key Dates
The holiest month of the Islamic year: the month of fasting, the month in which the Quran was first revealed, and the month containing Laylat al-Qadr (the Night of Power), a night better than a thousand months. Fasting during Ramadan is the fourth pillar of Islam.
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Eid al-Fitr falls on the 1st of Shawwal, the Festival of Breaking the Fast, one of the two great Islamic celebrations. The six voluntary fasts of Shawwal, combined with Ramadan, carry the reward equivalent to fasting the entire year.
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One of the four sacred months and a month traditionally devoted to preparation for Hajj. Hostilities were forbidden during this month, allowing pilgrims to travel safely.
The month of Hajj, one of the four sacred months and the month of the greatest annual gathering in Islam. The first ten days are described by the Prophet ﷺ as the most virtuous days of the year. Eid al-Adha (the Festival of Sacrifice) falls on the 10th.
Key Dates