According to the Engishiki, the Onie no matsuri Festival was solemnized in same year as the emperors' enthronement if it took place before July, but was solemnized in the following year if the enthronement was held after August.
延喜式によれば、天皇の即位がその年の7月以前の場合にはその年に、8月以降の場合には翌年に行われることになっていた。