Editing Islamic calendar (section)

===Pre-Islamic calendar===
{{Main|Pre-Islamic calendar}}
For central Arabia, especially [[Mecca]], there is a lack of epigraphical evidence but details are found in the writings of Muslim authors of the [[Abbasid]] era. Inscriptions of the ancient [[South Arabia]]n calendars reveal the use of a number of local calendars. At least some of these South Arabian calendars followed the [[lunisolar calendar|lunisolar system]]. Both [[al-Biruni]] and [[al-Mas'udi]] suggest that the ancient Arabs used the same month names as the Muslims, though they also record other month names used by the pre-Islamic Arabs.<ref name="EI2-Tarikh"/>{{which|date=March 2021}}

The Islamic tradition is unanimous in stating that Arabs of [[Tihamah]], [[Hejaz]], and [[Najd]] distinguished between two types of months, permitted (''ḥalāl'') and forbidden (''ḥarām'') months.<ref name="EI2-Tarikh"/> The forbidden months were four months during which fighting is forbidden, listed as Rajab and the three months around the [[hajj|pilgrimage]] season, Dhu al-Qa‘dah, Dhu al-Hijjah, and Muharram.<ref name="EI2-Tarikh"/> A similar if not identical concept to the forbidden months is also attested by [[Procopius]], where he describes an armistice that the Eastern Arabs of the Lakhmid al-Mundhir respected for two months in the [[summer solstice]] of 541 CE.<ref name="EI2-Tarikh"/> However, Muslim historians do not link these months to a particular season. The [[Qur'an]] links the four forbidden months with ''Nasī{{'}}'', a word that literally means "postponement".<ref name="EI2-Tarikh"/> According to Muslim tradition, the decision of postponement was administered by the tribe of [[Kinanah]],<ref name=Moberg2/> by a man known as the ''al-Qalammas'' of Kinanah and his descendants (pl. ''qalāmisa'').<ref name=Kitab/>

Different interpretations of the concept of ''Nasī{{'}}'' have been proposed.<ref>For an overview of the various theories and a discussion of the problem of "hindsight chronology" in early and pre-Islamic sources, see [http://etheses.dur.ac.uk/978/1/978.pdf?EThOS%20(BL) Maurice A. McPartlan, ''The Contribution of Qu'rān and Hadīt to Early Islamic Chronology'' (Durham, 1997)] {{Webarchive|url=https://web.archive.org/web/20131105220706/http://etheses.dur.ac.uk/978/1/978.pdf?EThOS%20(BL) |date=5 November 2013 }}.</ref> Some scholars, both Muslim<ref>Mahmud Effendi (1858), as discussed in Sherrard Beaumont Burnaby, ''[https://archive.org/details/elementsofjewish00burnuoft Elements of the Jewish and Muhammadan calendars]'' (London: 1901), pp. 460–470.</ref><ref>According to "Tradition", repeatedly cited by F.C. De Blois.</ref> and Western,<ref name="EI2-Tarikh">F.C. De Blois, "TA’RĪKH": I.1.iv.  "Pre-Islamic and agricultural calendars of the Arabian peninsula", ''The Encyclopaedia of Islam'', 2nd edition, '''X''':260.</ref><ref name=Moberg2>A. Moberg, "NASI'", ''The Encyclopaedia of Islam'', 2nd, VII: 977.</ref> maintain that the [[Pre-Islamic Arabia|pre-Islamic]] calendar used in central Arabia was a purely lunar calendar similar to the modern Islamic calendar. According to this view, ''Nasī{{'}}'' is related to the pre-Islamic practices of the Meccan Arabs, where they would alter the distribution of the forbidden months within a given year without implying a calendar manipulation. This interpretation is supported by Arab historians and lexicographers, like [[Ibn Hisham]], [[Ibn Manzur]], and the corpus of [[tafsir|Qur'anic exegesis]].<ref>{{Cite book|edition=4th|publisher=Al-maktaba al-tijāriyya|last=Muḥammad al-Khuḍarī Bayk|title=Muḥāḍarāt tārīkh al-Umam al-Islāmiyya|year=1935|pages=59–60|volume=2}}</ref>

This is corroborated by an early [[Sabaic]] inscription, where a religious ritual was "postponed" (''ns'w'') due to war. According to the context of this inscription, the verb ''ns'’'' has nothing to do with intercalation, but only with moving religious events within the calendar itself. The similarity between the religious concept of this ancient inscription and the Qur'an suggests that non-calendaring postponement is also the Qur'anic meaning of ''Nasī{{'}}''.<ref name="EI2-Tarikh"/> The ''[[Encyclopaedia of Islam]]'' concludes "The Arabic system of [Nasī'] can only have been intended to move the Hajj and the fairs associated with it in the vicinity of Mecca to a suitable season of the year. It was not intended to establish a fixed calendar to be generally observed."<ref>The Encyclopedia of Islam, 2nd edition, Index, p. 441.</ref> The term "fixed calendar" is generally understood to refer to the non-intercalated calendar.

Others concur that it was originally a lunar calendar, but suggest that about 200 years before the [[Hijra (Islam)|Hijra]] it was transformed into a [[lunisolar calendar]] containing an [[Intercalation (timekeeping)|intercalary month]] added from time to time to keep the pilgrimage within the season of the year when merchandise was most abundant. This interpretation was first proposed by the medieval Muslim astrologer and astronomer [[Abu Ma'shar al-Balkhi]], and later by [[al-Biruni]],<ref name=Kitab>[[Ja'far ibn Muhammad Abu Ma'shar al-Balkhi|Abu Ma'shar al-Balkhi]] (787–886), ''[http://gallica.bnf.fr/ark:/12148/bpt6k93171b.image.f166.langFR Kitab al-Uluf] {{Webarchive|url=https://web.archive.org/web/20110703090924/http://gallica.bnf.fr/ark:/12148/bpt6k93171b.image.f166.langFR |date=3 July 2011 }}'', ''Journal Asiatique'', series 5, '''xi''' (1858) 168+. {{in lang|fr|ar}}</ref><ref name="Nasi">{{cite book |url=https://archive.org/details/chronologyofanci00biru |last=al-Biruni |first=Abu Rayhan Muhammad ibn Ahmad |author-link= al-Biruni|translator-last= Sachau |translator-first=C. Edward |translator-link=Eduard Sachau|title="Intercalation of the Ancient Arabs", The Chronology of Ancient Nations |year=1879 |location=London |publisher=William H. Allen|pages=[https://archive.org/details/chronologyofanci00biru/page/13 13]–14, 73–74}}</ref> [[al-Mas'udi]], and some western scholars.<ref name=Moberg1>A. Moberg, "[https://books.google.com/books?id=9JQ3AAAAIAAJ NASI']", ''E.J. Brill's first encyclopaedia of Islam''.</ref> This interpretation considers ''Nasī{{'}}'' to be a synonym to the Arabic word for "intercalation" (''kabīsa''). The Arabs, according to one explanation mentioned by Abu Ma'shar, learned of this type of intercalation from the Jews.<ref name=Moberg2/><ref name=Kitab/><ref name="Nasi"/> The Jewish ''Nasi'' was the official who decided when to intercalate the Jewish calendar.<ref>Bab. Talmud, Sanhedrin, p. 11.</ref>{{Full citation needed|date=August 2022}} Some sources say that the Arabs followed the Jewish practice and intercalated seven months over nineteen years, or else that they intercalated nine months over 24 years; there is, however, no consensus among scholars on this issue.<ref>Bonner 2011, page 21.</ref>{{Full citation needed|date=August 2022}}