Editing Islamic calendar (section)

== Year numbering ==
{{Main|Hijri year}}
In pre-Islamic Arabia, it was customary to identify a year after a major event which took place in it. Thus, according to Islamic tradition, [[Abraha]], governor of Yemen, then a province of the Christian [[Kingdom of Aksum]] of [[Northeast Africa]] and [[South Arabia]], attempted to destroy the [[Kaaba]] with an army which included several elephants. The raid was unsuccessful, but that year became known as the ''[[Year of the Elephant]]'', during which Muhammad was born (surah [[al-Fil]]). Most equate this to the year 570 CE, but a minority use 571 CE.

The first ten years of the Hijra were not numbered, but were named after events in the life of Muhammad according to [[al-Biruni]]:<ref>Sherrard Beaumont Burnaby, [https://archive.org/details/elementsofjewish00burnuoft ''Elements of the Jewish and Muhammadan calendars''] (1901) 376.</ref>
# The year of permission.
# The year of the order of fighting.
# The year of the trial.
# The year of congratulation on marriage.
# The year of the earthquake.
# The year of enquiring.
# The year of gaining victory.
# The year of equality.
# The year of exemption.
# The year of farewell.

In {{Circa|638}} (17 AH), [[Abu Musa al-Ash'ari]], one of the officials of the [[Rashidun Caliphate|Rashid Caliph]] [[Umar]] ({{Reign|634|644}}) in [[Basra]], complained about the absence of any years on the correspondence he received from Umar, making it difficult for him to determine which instructions were most recent. This report convinced Umar of the need to introduce an era for Muslims. After debating the issue with his counsellors, he decided that the first year should be the year of Muhammad's arrival at Medina (known as Yathrib, before Muhammad's arrival).<ref>{{cite book | last1=Tillier | first1=Mathieu | chapter=Recording debts in Sufyānid Fusṭāṭ: a reexamination of the procedures and calendar in use in the first/seventh century | date=2019-04-11 | editor-last=Tolan | editor-first=John | title=Geneses: A comparative study of the historiographies of the rise of Christianity, Rabbinic Judaism, and Islam | pages=148–188 | location=New York | publisher=Routledge | isbn=978-1-351-11331-1 | last2=Vanthieghem | first2=Naïm | doi=10.4324/9781351113311-8 | url=https://halshs.archives-ouvertes.fr/halshs-02308264/file/Tillier-Vanthieghem-Recording%20debts-DEF.pdf | id={{HAL archive link|halshs-02308264v1}} | chapter-url=https://shs.hal.science/halshs-02308264/file/Tillier-Vanthieghem-Recording%20debts-DEF.pdf}}</ref> [[Uthman]] then suggested that the months begin with Muharram, in line with the established custom of the Arabs at that time. The years of the Islamic calendar thus began with the month of Muharram in the year of Muhammad's arrival at the city of Medina, even though the actual emigration took place in Safar and Rabi' I of the intercalated calendar, two months before the commencement of Muharram in the new fixed calendar.<ref name="WH"/> Because of the Hijra, the calendar was named the Hijri calendar.

F A Shamsi (1984) postulated that the Arabic calendar was never intercalated. According to him, the first day of the first month of the new fixed Islamic calendar (1 Muharram AH 1) was no different from what was observed at the time. The day the Prophet moved from Quba' to Medina was originally 26 Rabi' I on the pre-Islamic calendar.<ref>''Chronology of Prophetic Events'', Fazlur Rehman Shaikh (2001) p.52 Ta-Ha Publishers Ltd.</ref> 1 Muharram of the new fixed calendar corresponded to Friday, 16 July 622 CE, the equivalent civil tabular date (same daylight period) in the [[Julian calendar]].<ref>Sherrard Beaumont Burnaby, [https://archive.org/details/elementsofjewish00burnuoft ''Elements of the Jewish and Muhammadan calendars''] (1901) pp. 373–5, 382–4.</ref><ref>{{cite book | chapter=Table 1.2 Epochs for various calendars | chapter-url=https://books.google.com/books?id=cK1XDwAAQBAJ&pg=PA17 | page=17 | title=Calendrical Calculations | edition=Third | oclc=1137352777 | publisher=O'Reilly | first1=Nachum | last1=Dershowitz | first2=Edward | last2=Reingold | date=2018 | isbn=9781108546935 | access-date=21 March 2023 | archive-date=24 April 2023 | archive-url=https://web.archive.org/web/20230424000945/https://books.google.com/books?id=cK1XDwAAQBAJ&pg=PA17 | url-status=live}}</ref> The Islamic day began at the preceding sunset on the evening of 15 July. This Julian date (16 July) was determined by [[Astronomy in medieval Islam|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. For example, al-Biruni mentioned this Julian date in the year 1000 CE.<ref>al-Biruni, ''The chronology of ancient nations'', tr. [[C. Edward Sachau]] (1000/1879) 327.</ref> Although not used by either medieval Muslim astronomers or modern scholars to determine the Islamic epoch, the thin [[Lunar phase|crescent moon]] would have also first become visible (assuming clouds did not obscure it) shortly after the preceding sunset on the evening of 15 July, 1.5 days after the associated [[dark moon]] (astronomical [[new moon]]) on the morning of 14 July.<ref>{{cite web | url=http://eclipse.gsfc.nasa.gov/phase/phases0601.html | title=NASA phases of the moon 601–700 | url-status=dead | archive-url=https://web.archive.org/web/20101008214455/http://eclipse.gsfc.nasa.gov/phase/phases0601.html | archive-date=8 October 2010}}</ref>

Though [[Michael Cook (historian)|Michael Cook]] and [[Patricia Crone]] in their book ''[[Hagarism]]'' cite a coin from AH 17, the first surviving attested use of a Hijri calendar date alongside a date in another calendar ([[Coptic calendar|Coptic]]) is on a [[papyrus]] from [[Egypt]] in AH 22, [[PERF 558]].