حَدَّثَنَا إِسْحَاقُ بْنُ عِيسَى بْنِ الطَّبَّاعِ عَنْ أَبِي مَعْشَرٍ قَالَ وَقُتِلَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ يَوْمَ الْجُمُعَةِ لِثَمَانِ عَشْرَةَ مَضَتْ مِنْ ذِي الْحِجَّةِ سَنَةَ خَمْسٍ وَثَلَاثِينَ وَكَانَتْ خِلَافَتُهُ ثِنْتَيْ عَشْرَةَ سَنَةً إِلَّا اثْنَيْ عَشَرَ يَوْمًا
مسند امام احمد بن حنبل · Hadith 545
It was narrated that Abu Ma'shar said: 'Uthman (RA) was killed on the eighteenth of Dhul-Hiijah 35 AH. His caliphate lasted twelve years less twelve days.
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020