Japanese Imperial year

or "National calendar year" is a unique calendar system in Japan. It is based on the legendary founding of Japan by Emperor Jimmu in 660 BC.
"Kōki" emphasizes the long history of Japan and the Imperial dynasty.
History.
The Summer Olympics and Tokyo Expo were planned as anniversary events in 1940 ("Kōki 2600"); but the international games were not held because of the Second Sino-Japanese War.
The Imperial Japanese Army (IJA) and Imperial Japanese Navy (IJN) used the "Kōki" system for identification. For example, 
In Japan today, the system of counting years from the reign of Emperor Jimmu has been abandoned.