ʿUthman ؓ was killed on the eighteenth of Dhul-Hijjah 35 AH, His caliphate lasted twelve years less twelve days.
عَنْ أَبِي مَعْشَرٍ قَالَوَقُتِلَ عُثْمَانُ يَوْمَ الْجُمُعَةِ لِثَمَانِ عَشْرَةَ مَضَتْ مِنْ ذِي الْحِجَّةِ سَنَةَ خَمْسٍ وَثَلاثِينَ وَكَانَتْ خِلافَتُهُ ثِنْتَيْ عَشْرَةَ سَنَةً إِلا اثْنَيْ عَشَرَ يَوْمًا