Comment by prometheus76

Where did you find their process for recalculating the dates? The Japanese calendar was lunar and calculated locally until the 1600s in some areas, all the way up to the 1800s in other areas. How did the researchers line up the dates in the journals to astronomical data? How can they assume that when a Japanese journal said "first day of spring" that they actually meant the astronomical first day of spring, for example? I'd like to see the methodology the researchers used, but I didn't find anything in their paper about it.