Japanese date calculator (inc. months, days, etc.)

[Gabriel L]

As a point of interest, you may enjoy this website ("NengoCalc"), which is the best Japanese date calculator I have found. I was considering writing my own but this one appears to cover the bases.

 

We are all familiar (I hope) with the basics of reading nenki. However I am never wholly comfortable seeing nigatsu/hachigatsu (second/eighth month) translated as February and August. Of course this works as a sort of poetic shorthand, and it is somewhat accurate in the case of post-1872 dates (when Japan officially adopted the Gregorian calendar). But ignoring the fact that 二月 and 八月 were "auspicious" months for forging—meaning many swords signed thus were not necessarily forged in those months—the historical Japanese calendar does not correspond to the western months. For example, in the old calendar 二月 is closer to March—give or take a couple weeks—than February.

 

Unfortunately there is no simple way to match the old isolunar calendar to the modern Western date, as it varied constantly according to multiple arcane principles (including leap months, various astrological issues, etc.). Two sources, Tsuchihashi & Zöllner, wrote detailed tables which form the basis of NengoCalc.

 

I think this calculator may be of greatest use therefore when (probably out of curiosity) one wishes to translate a nenki which is obviously specific, e.g. 享保元年五月十一日 Kyōhō gannen gogatsu jūichinichi. Casually, and inaccurately, one might translate this as May 11, 1716. Using the calculator, however, we can see that the eleventh day of the fifth month of the first year of Kyōhō corresponds to June 30, 1716 (and a Tuesday, haha) in the Gregorian.

 

I can't imagine that this would have any significant relevance to our interest in the vast majority of cases, but it at least allows us to quote or translate certain long-form nenki with greater specificity and accuracy than we might have otherwise attempted. Cheers,

 

—G.

 

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EDIT: this site gives some more information on the difficulty of matching dates. It also appears to refer to NengoCalc, and includes the line "for dates Tenshô 10/9/18 (Oct. 4, 1582) and before, dates are in the Julian calendar." I tested it out and indeed this is the case, so be aware of the change!

[Guido]

Thanks, Gabriel! The University of Tübingen, Germany, had a similar website, and I was looking for an alternative after they pulled it!

[Markus]

Yep, thanks a lot for posting that Gabriel!

Translations like "May 11" of "五月十一日" have always a thorn in my side.

[echizento]

Very useful, thanks for posting it.

[Nobody]

If you can write/read basic Japanese, the following site may be very powerful for date conversion. I often use the site. Unfortunately there seems to be no English version of it.

Ref. http://maechan.net/kanreki/

[Gabriel L]

Ah, that site is indeed very good… includes separate fields for Julian & Gregorian, you can go west > east or east > west, etc.

 

Thanks for posting it, it is easy to use even if you do not know much Japanese.