[Retric]

Astronomical events like eclipses get recorded and can be extrapolated backwards to precisely line up historic calendars. Similarly, major events like huge earthquakes can be correlated between different historic calendars.

Eventually you go back far enough and this breaks down, but we are talking recent history here.

[prometheus76]

You're assuming the researchers used earthquakes or astronomical events to correlate their date calculations, but they make no such claim. They do not explain their methodology for converting the historical calendar dates into Gregorian dates at all. Why should we give them the benefit of the doubt? They've included their dataset, but they haven't included their methodology for determining the Gregorian dates, yet their whole claim is that the dates are getting earlier and earlier. The line trending down also correlates with Japan converting to the Gregorian calendar in 1868. Why isn't that mentioned in their paper? If their methodology for converting historical dates is faulty or poor, that methodology could also account for the line appearing to move down starting in the mid-1800s.

They should be transparent about it and they weren't, and a lot of people here seem to be willing to just trust them and their methodology, but I can't figure out what's scientific or transparent about that. Isn't peer review supposed to catch and correct these types of issues before publication? And if not, shouldn't they be transparent enough in sharing their methodology that the concerns raised by amateur idiots like myself would be easily addressed, or at least accounted for?

[Retric]

These are hardly the first researches to want to correlate Japan’s dates with the Gregorian calendar. If you think the historic record is so wrong then feel free to do some original research and prove it, but don’t assume people are idiots.

Anyway, you have clearly already decided the issue in your own mind and are looking to justify it. So, no I am not going to waste my time providing evidence you can look up if you’re willing to consider the possibility you’re wrong then dare to do it yourself.

[prometheus76]

I feel the exact same way. They didn't share their methodology, and their claims hinge on the methodology they used for converting the dates. I'm not accusing them of anything. I'm asking to see their methodology. You are the one who is giving them the benefit of the doubt and assuming they did it correctly, which is antithetical to peer-reviewed science.

[Retric]

They didn’t need to do the correlation, other people have already done the leg work.

You’re effectively complaining they didn’t show their work when using dates from the Roman etc calendar. Historians really care about getting dates correct and have done extensive work to line up each historical calendar where possible.