Abdullah bin Muhammad bin Aqil says that in 35 AH, Sayyiduna Uthman (may Allah be pleased with him) was martyred, and five years of trial passed, out of which Sayyiduna Imam Hasan (may Allah be pleased with him) was also caliph for four months.
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 550
Hadith Gradingحکم دارالسلام:إسناده منقطع، عبدالله ابن محمد بن عقيل لم يدرك عثمان. قاله أحمد شاكر