The oldest recorded eruption of Mount Fuji (Traditional Japanese date: Sixth day of the seventh month of the first year of the Ten'o (天応) era).

Mount Fuji is an active stratovolcano located on the Japanese island of Honshu, with a summit elevation of 3,776.24 m. It is the highest mountain in Japan, the second-highest volcano on any Asian island, and seventh-highest peak of an island on Earth.

Japanese calendar types have included a range of official and unofficial systems. At present, Japan uses the Gregorian calendar together with year designations stating the year of the reign of the current Emperor. The written form starts with the year, then the month and finally the day, coinciding with the ISO 8601 standard.

July 31 is the 212th day of the year in the Gregorian calendar; 153 days remain until the end of the year.