Imam al-Layth bin Sa'd (may Allah have mercy on him) said: Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with him) passed away in the year 60 AH, when four nights of Rajab had passed. Ibn Kathir said: "And his age was somewhat over seventy, up to eighty years."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16728