Date of the Day of the Siege
Regarding the day in which Hazrat Uthman’s (ra) martyrdom took place, it is said that he was martyred on the 17th or 18th of Dhul Hijja 35 AH, on a Friday. According to Abu Uthman Nahdi, Hazrat Uthman (ra) was martyred in the middle days of Ayam-e-Tashreeq, i.e. 12 Dhul Hijja. However, according to Ibn Ishaq, Hazrat Uthman (ra) was martyred 11 years, 11 months and 22 days after the martyrdom of Hazrat Umar (ra) and 25 years after the demise of the Holy Prophet (sa).
(Ibn Abd al-Barr, Al-Isti‘ab fi Ma‘rifat al-Ashab, Vol. 3, Uthman (ra) bin Affan [Beirut, Lebanon: Dar al-Kutub al-Ilmiyyah, 2002], p. 159)
According to another narration, Abdullah bin Amr bin Uthman relates that Hazrat Uthman (ra) was martyred at the age of 82 after the Asr prayer on Friday 18 Dhul Hijja 36 AH. And he was fasting on the day he was martyred. According to Abu Ma‘shar, Hazrat Uthman (ra) was 75 years of age at the time of his martyrdom.
(Ibn Saad, Al-Tabaqat al-Kubra, Vol. 3, Uthman (ra) bin Affan [Beirut, Lebanon: Dar Ihya al-Turath al-Arabi, 1996], p. 43)