ENOfficial
It was narrated that ‘Abdullah bin Muhammad bin `Aqeel said: `Uthman (رضي الله عنه) was killed in 35 AH and the fitnah (turmoil) lasted for five years including four months of al-Hasan`s rule.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا زَكَرِيَّا بْنُ عَدِيٍّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَمْرٍو، عَنْ عَبْدِ اللَّهِ بْنِ مُحَمَّدِ بْنِ عَقِيلٍ، قَالَ قُتِلَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ سَنَةَ خَمْسٍ وَثَلَاثِينَ فَكَانَتْ الْفِتْنَةُ خَمْسَ سِنِينَ مِنْهَا أَرْبَعَةُ أَشْهُرٍ لِلْحَسَنِ رَضِيَ اللَّهُ عَنْهُ.
sunnah.com