Islamic Lunar Calendar: The Origins of Ramadan’s Seasonal Drift

July 24, 2014

Islam as a religion does not have a scripturally sanctioned calendar, nor is there a Sunnah or a Prophetic tradition suggesting one.  In Pre-Islamic Arabia there was a traditional 12-month calendar based on lunar phases with an intercalary month, referred to as an-nasī,ʾ ‘postponing’.  The purpose of the intercalary month was to synchronize the lunar calendar with the solar cycle in order to achieve a more consistent relationship between the months and the seasons of the year. 

According to Abū Rayḥān al-Bīrūnī, the great 11th century Muslim scholar, this synchronization was necessary to accommodate, along with other things, the scheduling of seasonal trade cycles with annual pre-Islamic Hajj pilgrimages.[i]  Even though the season and the calendar are no longer in sync today, the names of the months, nonetheless, reflect the pre-Islamic seasonal changes such as rabi’, ‘spring,’ jumada, ‘summer,’ ramadan, ‘parched heat,’ dhul hijja, ‘pilgrimage, etc.[ii] indicating that some of today’s Islamic rites and rituals may not only have roots in pre-Islamic Arab traditions, but they were ordained within the existing cycle of the pre-Islamic or Jahiliya calendar that did have the occasional 13th month.[iii]

The Jahiliya calendar was not reckoned from some mythical and pivotal event in centuries past, but with some contemporary event of significance.  At the time of the Prophet it was reckoned from an event that coincided with his birth and was known as the Year of the Elephant or ʿĀmu l-Fīl, the year approximately 569 or 570 CE. The name is derived from the Christian Yemenite King Abraha’s march on Mecca with war elephants in a failed attempt to destroy the Ka’ba.  Thus, the Prophet migrated to Yathrib (later Medina) in the 52nd Year of the Elephant or ʿĀmu l-Fīl.

Contrary to the common belief, Muslims did not start their new calendar on the year of the hijra or migration to Medina in 622 CE nor did they reckon their calendar from the hijra.  While the hijra certainly surpassed the Year of the Elephant in significance for the small Muslim community, they continued to use the established calendar of the Jahiliya period.  As there was no Islamic calendar during the life of the Prophet Muhammad, the first ten years of hijra, as a new beginning,[iv] were not numbered, but named after events in the life of the Prophet.[v] The Prophet was, however, strongly opposed to the insertion of the intercalary month, a position that was subsequently validated by Qur’anic injunctions.[vi]

Understanding the reasons behind the prohibition of the intercalary month of an-nasī by the Prophet demands an accommodation of reason with revelation and this requires a quick look at the prevalent socio-political environs of his time.  Sixth century Arabia was caught up in devastating inter-tribal conflicts known as the jahiliya, mildly translated as the age of ignorance—a society perpetually at war with each other except during four sacred months of the year or the months of haram, ‘prohibition’: Rajab, Dhu al-Qi'dah, Dhu al-Hijjah, and Muharram or the 7th, 11th, 12th, and 1st months of the year. Aside from the 7th month, the other three months provided a sold three-month respite from the torment of war, except during the years when the intercalary month was added.  Leaders of the warring tribes sometimes arbitrarily chose to add the intercalary month in one year instead of another when it was advantageous to their war plans.  In an attempt to reduce violence and prolong peace, the Prophet took a strong position against nasi, this additional month of war and emphasized the significance of the prohibition one last time during his farewell sermon:

Certainly the Nasi' is an impious addition, which has led the infidels into error. One year they authorise the Nasi', another year they forbid it. They observe the divine precept with respect to the number of the sacred months, but in fact they profane that which God has declared to be inviolable, and sanctify that which God has declared to be profane.[vii] 

Aside from the epistemological reasons why Muhammad’s religion is called Islam, ‘peace,’ its naming also reflects the Prophet’s opposition to war in the reality of his time.  Evidently peace was more conducive to the success of his prophetic mission, so much so that at times like at Hudaybiyyah the Prophet risked a rebellion by his followers due to his willingness to accept the unfair stipulations of the treaty, his agreeing to give up the Hajj pilgrimage to Ka’ba, and even disclaiming his prophetic title on the treaty document. He threw down the gauntlet in return for a mere commitment from his opponents for a lasting peace.  Evidently, his risky strategy paid off as he won a 10-year peace treaty with the Quraish.[viii]

This characteristically strong active advocacy for peace by the Prophet suggests that the rationale for his prohibition of the intercalary month of an-nasī must have been aimed at having longer intervals of peace without the intermittent threat of war, and if Divine revelation had to sanction it, so much the better.  This was why astronomy was allowed to determine the natural rotational lunar cycle without the interruption of intercalary months.

It wasn’t until 638 CE, during the time the Caliph Omar, that the need to introduce an Islamic era was felt. The need was triggered by an event in Basra where Abu Musa Ash’ari, a great scholar and an officials of the Caliphal state drew the attention of Caliph Omar to an improperly dated debenture or IOU which was payable in the month of Sha’ban, but without any indication as to whether it referred to the previous or the coming month of that name.[ix]

Caliph Omar convened a council that recommended the establishment of an Islamic calendar to be reckoned from the epochal event of hijra.  However, in order to keep with the traditional numerical sequence of months within the year, it was decided, at the suggestion of Uthman ibn ‘Affan, that the year of the hijra begin with the month of Muharram instead of starting the calendar on the actual dates of departure from Mecca, 26 Safar, or arrival in Medina, 12th Rabiul Awwal[x] (June 13 CE 622 and July 22 CE 622 respectively). As a result, on the 16th year of Muhammad’s hijra or migration to Medina the first year of the new Islamic calendar was established and made retroactive to the month of Muharram in the year of hijra.  Thus the first day of the first month of the Islamic Hijri Calendar was 1 Muharram 1 AH, After Hijra (Latin designation AH, Anno Hegirae) or Friday, 16 July 622 CE.[xi] 

But Islam’s desert ethnic character soon gave way to cultural splendor as it became a religious-cum-civilizational global force. The admission of other societies and nations in the wider reaches of the three continents into the tent and tenants of Islam turned it into a culture of confluence that sprawled in lands far beyond the Arabian deserts where the environment was not in congruence with the rotational lunar calendar that had no regard for the change of distinct seasonal changes. This was particularly critical in regards to levying annual taxes and creating budgets that depended on revenues from a largely agrarian populace.

(Stay tuned for Part II)

[i] Abū al-Rayhān Muhammad ibn Ahmad al-Bīrūnī (973-1048), known as Alberonius in Latin is regarded as one of the greatest scholars of the medieval Islamic era and was well versed in physics, mathematics, astronomy, and natural sciences, and also distinguished himself as a historian, chronologist and linguist. He spent a large part of his life in Ghazni, Afghanistan, capital of the Ghaznavid dynasty.

Wikipedia Abu Rayhan al Biruni.

[ii] Four of the twelve Hijri months are considered sacred, although there is disagreement over the designated months, such as between proponents for the sequences {7,11,12,1} vs. {12,1,2,3}. The twelve Hijri months are named as follows in Arabic:  Muḥarram, "forbidden,” Ṣafar, "void," Rabīʿ I, "the first spring," Rabīʿ II or Rabīʿ al-Ākhir, "the second (or last) spring," Jumādā I, "the first month of parched land" of the pre-Islamic "summer," Jumādā II or Jumādā al-Ākhira, "the second (or last) month of parched land," Rajab, "respect," or "honor,” Shaʿbān, "scattered,” Ramaḍān, "scorched,” Shawwāl, "raised,” Dhū al-Qaʿda, "the one of truce, and ”Dhū al-Ḥijja, "the one of pilgrimage."

[iii] The 13 months of the Jahiliya calendar were in order: mu’tamir, najir, khawwan, wabsan, hanin, rubba, al-‘asam, ‘adhil, natiq, wa’l, warnah, burak, an-nasi.

Source: Al-muntakhab min gharib kalam al’arab of Abu al-hassan ‘ali bin al-hasan bin al-husayn al-huna-i ad-dusa (d. 309 AH/921 CE) and Lisan al’arab of Ibn Manzur (d. 711 AH/1311 CE).  

[iv] In respect to an emphasis on ‘a new beginning,’ Prophet Muhammad’s new movement in the new state of Medina may well have inspired the French revolutionaries. The French Revolutionary Calendar (calendrier révolutionnaire français) adopted during the French Revolution, and used by the French government between 1793-1805 aimed at removing all religious and royalist influences from the calendar, as a sign of reform and cutting off from the trappings of the ancien régime.  Also, just like the ten years of the Prophet’s life in Medina that were not numbered, but named after concepts, the French revolutionaries also named the months and days after concepts in life and nature. Wikipedia French Republican Calendar.

[v] Al-Bīrūnī lists the first ten years of the hijra in the life of the Prophet in order as the years of permission, the order of fighting, the trial, congratulation on marriage, the earthquake, enquiring, gaining victory, equality, exemption, and farewell.

Wikipedia Abu Rayhan al Biruni.

[vi] Qur’anic references to calendar: [2:189] “They ask you about the phases of the moon! Say, "They provide a timing device for the people, and determine the time of Hajj. ... [6:96] At the crack of dawn, He causes the morning to emerge. He made the night still, and He rendered the sun and the moon to serve as calculation devices. Such is the design of the Almighty, the Omniscient. [9:36] "Lo the number of the months with God is twelve months.", [10:5] He is the One who rendered the sun radiant, and the moon a light, and He designed its phases that you may learn to count the years and to calculate. GOD did not create all this, except for a specific purpose. He explains the revelations for people who know. Source: Comprehensive Quran Search.

[vii] The farewell sermon delivered shortly before Prophet Muhammad passed away instinctively summarized his prophetic mission and was delivered on 9 Dhu al-Hijja 10 AH (Julian date Friday 6 March 632 CE) on Mount Arafat during the pilgrimage to Mecca. This translation is by Sherrard Beaumont Burnaby

[viii] Wikipedia - Treaty of Hudaybiyyah.

[ix] Abdus Sattar Ghazali. The Calendars.

[x] Following is the chronology of the hijra of the Prophet the city is referred to as Medina, and the region surrounding it as Yathrib.




Day 1


26 Safar AH 1

(13 June 622)

Left home in Mecca. Hid three days in the Cave of Saur south of Mecca.

Day 9


1 Rabi' I AH 1

(17 June 622)

Left the environs of Mecca. Traveled north to the region of Yathrib.

Day 16


12 Rabi' I AH 1

(27 June 622)

Arrived at Quba’ near Medina.

Alvi, Ibn Sa'd, Abu Ja'far and Ibn Hisham on the above dates. The hypothetical dates in the retro-calculated Islamic calendar extended back in time will differ from the actual dates as they would have been on the modern international Gregorian calendar.

Wikipedia – Hijra (Islam).

[xi] This Julian date (16 July) was determined by medieval Muslim astronomers by projecting back in time their own tabular Islamic calendar, which had alternating 30- and 29-day months in each lunar year plus eleven leap days every 30 years.