Japan Calendar Systems Zodiac Iroha Ordering Schemes

皇紀 koki "imperial era"
National Era System
During the Meiji Restoration in 1868, the national era or imperial year calendar system was initiated, which counted years from the founding date of the imperial dynasty, 660 B.C. Type numbers for service aircraft were derived from the last one or two digits of the year; i.e., Type 96 Fighter indicates a fighter accepted for service in the year 2,596 (Gregorian 1936). This calendar system was used through the end of World War II.

大正時代 Taisho jidai "period of great righteousness"
Taisho Era System
In 1912, Yoshihito became emperor of Japan. He ruled from 30 July 1912 to 25 December 1926, which became known as the Taisho Era. The Taisho Era calendar system counts years starting from 1912. Aircraft accepted for service during this period received a Type designation using the Taisho Era year (see table below).

昭和時代 Showa jidai "period of enlightened peace"
Showa Era System
In 1926, Hirohito became emperor of Japan. He ruled from 25 December 1926 to 7 January 1989, which became known as the Showa era. The Showa Era calendar system counts years starting from 1926. Imperial Japanese Navy aircraft specifications used the Showa Era year (see table below).

The following table provides a calendar cross-reference for years starting from 1912 up to the World War II era, along with aircraft Type examples:

Gregorian National/Imperial Taisho Showa Example Aircraft Designation or Specification 1912 2,572 1 -- Type 1 1913 2,573 2 -- Type 2 1914 2,574 3 -- Type 3 1915 2,575 4 -- Type 4 1916 2,576 5 -- Type 5 1917 2,577 6 -- Type 6 1918 2,578 7 -- Type 7 1919 2,579 8 -- Type 8 1920 2,580 9 -- Type 9 1921 2,581 10 -- Type 10 1922 2,582 11 -- Type 11 1923 2,583 12 -- Type 12 1924 2,584 13 -- Type 13 1925 2,585 14 -- Type 14 1926 2,586 15 1 Type 15 or Type 86; 1-Shi 1927 2,587 -- 2 Type 87; 2-Shi 1928 2,588 -- 3 Type 88; 3-Shi 1929 2,589 -- 4 Type 89; 4-Shi 1930 2,590 -- 5 Type 90; 5-Shi 1931 2,591 -- 6 Type 91; 6-Shi 1932 2,592 -- 7 Type 92; 7-Shi 1933 2,593 -- 8 Type 93; 8-Shi 1934 2,594 -- 9 Type 94; 9-Shi 1935 2,595 -- 10 Type 95; 10-Shi 1936 2,596 -- 11 Type 96; 11-Shi 1937 2,597 -- 12 Type 97; 12-Shi 1938 2,598 -- 13 Type 98; 13-Shi 1939 2,599 -- 14 Type 99; 14-Shi 1940 2,600 -- 15 Type 100 (Army) or Type 0 (Navy); 15-Shi 1941 2,601 -- 16 Type 1; 16-Shi 1942 2,602 -- 17 Type 2; 17-Shi 1943 2,603 -- 18 Type 3; 18-Shi 1944 2,604 -- 19 Type 4; 19-Shi 1945 2,605 -- 20 Type 5; 20-Shi

Japanese Zodiac
A portion of the Japanese zodiac (the "Ten Stems") was used by the Imperial Japanese Army and Navy to signify modifications to a basic design. These terms (ko, otsu, hei, tei, etc.) are sometimes translated into English as "a," "b," "c," "d," etc. However, this does not fully reflect the original Japanese context. This table illustrates the relationships of these terms within the Japanese zodiac:

Element Reading Yin/Yang Stem Pronounciation (romaji) Wood 木 ki Yang (e) 甲 ko Yin (to) 乙 otsu Fire 火 hi Yang (e) 丙 hei Yin (to) 丁 tei Earth 土 tsuchi Yang (e) 戊 bo Yin (to) 己 ki Metal 金 kane Yang (e) 庚 ko Yin (to) 辛 shin Water 水 mizu Yang (e) 壬 jin Yin (to) 癸 ki

Examples:
IJA: Ki-61-I-Ko, Ki-61-I-Otsu, Ki-61-I-Hei, Ki-61-I-Tei are the designations of four sub-variants of the Kawasaki Ki-61-I Hien (Army Type 3 Fighter). These are sometimes translated as Ki-61-Ia, Ki-61-Ib, Ki-61-Ic, Ki-61-Id.
IJN: A6M3 Type 0 Carrier Fighter Model 32a; A6M5c Type 0 Carrier Fighter Model 52 Hei.

Iroha
The Iroha is an ancient Japanese poem that contains each Japanese syllable exactly once and was often used as an ordering method.

Hiragana Pronounciation (romaji) Ordering Translation いろはにほへと i ro ha ni ho he to 1 - 7 Even the blossoming flowers ちりぬるを chi ri nu ru wo 8 - 12 Will eventually scatter わかよたれそ wa ka yo ta re so 13 - 18 Who in our world つねならむ tsu ne na ra mu 19 - 23 Is unchanging? うゐのおくやま u wi no o ku ya ma 24 - 30 The deep mountains of vanity-- けふこえて ke fu ko e te 31 - 35 We cross them today あさきゆめみし a sa ki yu me mi shi 36 - 42 And we shall not see superficial dreams ゑひもせす we hi mo se su 43 - 47 Nor be deluded.

Examples: Yokosho I-go Ko-gata Seaplane Trainer; IJN long-range submarines designated "I", coastal submarines designated "Ro" and training submarines designated "Ha."

[

Japan

]

[

Home

|

About

|

Contact

|

Top

]