dating was used as early as 1872, shortly after Japan adopted the
Gregorian calendar and was popular during the life of the
Meiji Constitution (1890–1947). Its use was promoted by the scholars of
kokugaku in the late 19th century. The
Summer Olympics and Tokyo Expo were planned as
anniversary events in 1940 (); but the international games were not held because of the
Second Sino-Japanese War. The
Imperial Japanese Army (IJA, from 1927) and
Imperial Japanese Navy (IJN, from 1929) used the system for
identification. For example many Japanese names circa
World War II use imperial years: • The IJA's
Type 92 battalion gun was called "ninety-two" because its design was completed in 1932, and the 2592nd year since the first Emperor of Japan was 1932 (). • Japan's wartime cipher machine was named the
System 97 Printing Machine for European Characters because it entered service in 1937 (). • The Mitsubishi A6M (Navy Type 0 Carrier Fighter), colloquially called the "Zero" by allied forces, entered service in 1940 (). The
Proclamation of Indonesian Independence (1945) used the imperial year (). In Japan today, the system of counting years from the
reign of
Emperor Jimmu is used in some judicial contexts. The existing law determining the placement of
leap years is based on the years, using a formula that is effectively equivalent to that of the Gregorian calendar. is also used in
Shinto context. ==See also==