View source for Belisarius' encounter with the Hajj, eighty years before the rise of Islam, 541 CE

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<font size=-2>'''Table 5. Pre-Islamic Calendar after Commutation of Third Sacred Month (Dhu al-Qa'dah for Shawwaal)'''</font>

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<td bgcolor="#cccccc">1. Safar al-Muzaffar صف</td>
<td bgcolor="#cccccc">7. Tishrei תשרי</td>
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<td>2. Rabi al-Awal ربيع الأول</td>
<td>8. Cheshvan חשוון</td>
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<td>3. Rabi al-Thaani ربيع الآخر</td>
<td>9. Kislev כסלו</td>
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<td>4. Jumaada al-Awal جمادى الأول</td>
<td>10. Tevet טבת</td>
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<td>5. Jumaada al-Thaani جمادى الثاني</td>
<td>11. Shevat שבט</td>
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<td>6. Rajab al-Murajjab رجب</td>
<td>12. Adar אדר</td>
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<td bgcolor="#cccccc">7. Shabaan al-Muazzam شعبان</td>
<td bgcolor="#cccccc">1. Nisan ניסן</td>
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<td>8. Ramadhaan al-Mubarak رمضان</td>
<td>2. Iyyar אייר</td>
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<td>9. Shawwaal al-Mukarram شوّال</td>
<td>3. Sivan סיוון</td>
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<td bgcolor="#cccccc">10. Dhu al-Qa'dah ذو القعدة</td>
<td bgcolor="#cccccc">4. Tammuz תמוז</td>
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<td bgcolor="#cccccc">11. Dhu al-Hijjah ذو الحجة</td>
<td bgcolor="#cccccc">5. Av אב</td>
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<td>12. Muharram al-Haraam محرّم</td>
<td>6. Elul אלול</td>
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In the year 541 CE. Belisarius summoned a council of war against Persia. Two Roman officers in command of Syrian garrisons declined to follow the army to Nisibis, on the plea that their absence would leave Syria and Phenicia exposed to the attacks of Mundzir. Belisarius argued that as the summer solstice was at hand, when the Arabs devoted two months to the rites of their religion without resorting to arms, there was no cause for apprehension; and he promised to let them go when that period was expired. These were the months of Meccan pilgrimage: and hence we learn that Mundzir and the majority of his Arabs followed the religion of the Hejaz.<ref>The Life of Mahomet, William Muir, Esq., Smith, Elder, & Co., London, 1861, Chapter III, Section 4.</ref> 

The summer solstice June 21, 541 CE would have fallen on 10th of Jumaada al-Thaani according to the strictly Lunar Calendar now in Islamic use, six months too early for the Hajj pilgrimage.  This means that intercalation must have been in use in the years before the Prophet. If we assume the Jewish intercalation currently used, the solstice would have fallen on Dhu al-Qa'dah (Tammuz) – the first of the "two months".  If we assume a simple 3 year intercalation the solstice would have fallen on 10th of Dhu al-Hijjah, the correct date.

We also see from this that the third sacred month had been commutated, that is, Shawwaal had been exchanged with Dhu al-Qa'daha.  This allowed for a convenient contiguous period of cessation of hostilities, see Table 5.

==References==
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[[Category:Islam and Judaism]]
[[Category:The Islamic Jewish Calendar]]