Change of era
- 1781 Tenmei gannen (天明元年): The new era name of Tenmei (meaning "dawn") was created to mark the enthronement of Emperor Kōkaku. The previous era ended and the new one commenced on the second day of the fourth month in what had been An'ei 11.
As is customary for choosing nengō, the name was selected from a passage in a historical Chinese text. In this case, the text was Classic of History (書経) (also quoted in The Great Learning (大學)), more specifically from the first of the King Tai Jia (大甲) chapters. It says: "先王顧諟天之明命..." meaning "The former king kept his eye continually on the bright requirements of Heaven, [and...]." This is continued with a description of reverence, virtue, and prosperity for the lands. From this, the two characters 天 and 明 were selected.