(author here) If you look into the academic papers published by Aono, you'll see that he goes into a fair bit of detail regarding both of those points: how he

(author here) If you look into the academic papers published by Aono, you'll see that he goes into a fair bit of detail regarding both of those points: how he determined consistent historical peak bloom dates, and how he calculated consistent Gregorian dates from the ancient Japanese dates. Not being an expert in these things myself, I consciously chose not to try and explore them myself in much detail.