Heisei Era will End 通訳の年号変換

Japanese follows English.　英語の後に日本語が続きます。

As you may know, the Heisei Era will end on April 30 next year. For those who aren't familiar with the Japanese era system, we, the Japanese, have a specific name for a period during which an emperor reigns and so, when a new emperor accedes to the throne, the name of the period also changes. As the current 125th Emperor Akihito will abdicate on April 30 next year, the Heisei Era, reigned by him, will also end on that day. The names of the recent eras and their periods are as follows: 

Heisei era:  January 8, 1989 to April 30, 2019, reigned by Akihito
Showa era: December 25, 1926 to January 7, 1989, reigned by Hirohito
Taisho era: July 30, 1912 to December 24, 1926, reigned by Yoshihito
Meiji era: January 25, 1868 to July 29, 1912, reigned by Mutsuhito

Emperors don't have last names and we don't know why for sure. But it's said that as last names used to be given by the emperor of the period, they have had nobody giving one to them or that as male succession has continued in an unbroken line for 125 generations from the first reign, they haven't needed to have last names to differentiate themselves from others. 

I'm not interested in the reason for their not having last names, but in an issue for interpreters, i.e., they have to translate the Japanese year to the Gregorian calendar year in a second while interpreting! This happens because most Japanese use the Japanese calendar year, so when a speaker says "Heisei 30 (i.e., 2018)," the interpreter has to immediately translates the year to the Gregorian year by subtracting 12 (i.e., 30-12=18, meaning 2018). In other words, interpreters have to memorize how many years they need to add or subtract for each era, i.e., for Heisei add 88 or subtract 12, Showa add 25, Taisho add 11 and Meiji add 67 or subtract 33, and do such additions/subtractions while interpreting.

Whatever the name of the new era will be, interpreters/translators will have to remember one more formula, i.e., adding 18 to the Japanese year to convert it to the Gregorian year! 

来年元号が変わる。新元号のシステム対応が大変なことは知られているが、密かに大変なのは通訳の頭の中である。言語変換のみならず、元号を瞬時に西暦に変換するための足し引きをやっているのをご存じだろうか。つまり、平成は12引く、昭和は25足す｡｡｡といった具合。言葉だけでも大変なのに、算数もやるから大変なんです。メートルとフィート、セルシウスとファーレンハイトも同じで、6フィートと言われても大きいかどうかぴんとこないし、華氏100度と言われても暑いかどうかぴんとこないが、こちらは変換せずにそのまま言ってもまあ大丈夫。でも、元号だけはそうはいかないのです。新元号の場合は「18足したら西暦」。お疲れ様です！