About Sonohini

General Information

You're probably wondering ‘Why spend so much effort to build a date conversion site that nobody needs?’ Excellent question. I built this mostly just because I wanted to, but also because existing tools for converting Japanese dates to Western dates are either incomplete, inaccurate, or difficult to use on modern mobile devices. Also, finding accurate information in English about Japanese eras and emperors on the internet is extremely difficult, if not impossible. I hope my efforts have made it easier.

Dates on the Site

Currently all dates on the site are expressed as Western dates. All dates before 1582 are Julian Calendar dates and all dates after 1582 are Gregorian Calendar dates. Most dates before the 6th century are either approximate or based on legends of dubious accuracy.

Before the Meiji Period, Japan used era names and a variety of lunar calendars to record dates. Era names were assigned by the reigning emperor and could be changed at the emperor's will. Most years had 12 months, but an occasional 13th month was added to keep the calendar inline with the seasons, much like the current Gregorian Calendar does during leap years. A typical date from pre-Meiji Japan might look something like this: 元暦2年8月14日, 2nd year of the Bunji Era, 8th month, 14th day. Due to the use of a lunar calendar, traditional Japanese dates were one to two months behind their western counterparts. The previous example (Bunji 2, 8th month, 14th day) corresponds to August 9th, 1185 in the Gregorian Calendar, almost a full month off. During the Meiji Restoration, the old calendar system was dropped in favor of the Gregorian Calendar and the era name system was changed so that an era name lasted the entirety of an emperor's reign.

Note that many sites on the internet incorrectly use the Japanese date as the Western date (i.e. 元暦2年8月14日 is the same as 8-14-1185) leading to misunderstanding and inaccuracy. I have done my best to find accurate conversions to help resolve this problem.

Sources and References

Dates and information about Japanese eras and emperors were taken from the following sources:

Contact Information

If you found an error in the site, disagree with the information presented, have a suggestion for the site, or just want to chat about the weather, feel free to contact me using the contact form. If you found a bug or are having problems, use the contact form to contact me or report the bug here.

Technical Information About the Site

This site was originally a 60 line python script that I wrote so I could convert Japanese dates in the command line. The site as you see it today is a result of much head scratching and several rebuilds.

The first web version of this site was my 2014 cs50x final project.

Built on the Laravel php framework.

Proudly hosted on DigitalOcean.