In this government, the Emperor ruled the politics directly without regents or chancellors [chief advisers to the Emperor] as a matter of form, and his time, which was admired as 'Engi no chi (the peaceful era of Engi),' continued for 34 years; however, it is said that the Shotai no Hen (the Shotai Incident), which occurred in 901 when SUGAWARA no Michizane's position was lowered to Dazai no Gon no Sochi after Tokihira made a false charge against him, was the biggest mistake of the government ruled by a son of Heaven.
その治世は34年の長きにわたり、摂関を置かず形式上の親政を行っていたため、後世「延喜の治」と崇められたが、昌泰4年（901年）、時平の讒言を聞き菅原道真を大宰権帥に貶めた昌泰の変は、聖代の瑕と評されることであった。