The following description of the Japanese calendar and date systems was originally published in Tactical and Technical Trends, No. 21, March 25, 1943. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

JAPANESE DATE SYSTEMS It may be useful to recapitulate the systems now used by the Japanese in writing dates. a. According to mythology, the Japanese Empire was founded in the year 660 B.C., and it is from this date that Japanese years are calculated in one system of writing dates. For example, our 1940 is the Japanese 2600, and so on. Type numbers for Japanese aircraft and various other military equipment are often derived from this system of dates. The last two digits of the year concerned, until and including 2599 (1939), are used for the type number; from 2600 (1940) onward, the last digit alone is used. Type "97" was adopted in the year 2597 (1937), Type "0" (zero) in 2600 (1940), Type "1" in 2601 (1941), and so on.* b. In more general usage, however, is the practice (in use since 1868) of numbering years from the start of each Emperor's reign. A name is chosen for each reign, and a given year is referred to by the number of years that have elapsed since the reign started. The name of the reign of the present Emperor, which began in 1926, is Showa (Enlightened Peace); 1943 is thus the 18th year of Showa, or more simply "Showa 18." c. The Western or Christian calendar is also in common use among the Japanese. *For the use of the term "Zero" as applied to aircraft, see Tactical and Technical Trends, No. 19, p. 1.

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