Emperor Seiwa
10 July 858 (Ten'an 2, 27th day of the 8th month): In the 8th year of Montoku-tennō 's reign (文徳天皇8年), the emperor abdicated.  The succession (senso) was received by a his son.  Then Emperor Seiwa is said to have acceded to the throne (sokui).  This was confirmed in ceremonies.