https://www.jstage.jst.go.jp/article/timestudies/1/0/1_17/_a...
This is the paper. It did describe the challenges of inferring the full-bloom date from old literary work. But the calendar conversion is not one of the challenges.
This is the paper. It did describe the challenges of inferring the full-bloom date from old literary work. But the calendar conversion is not one of the challenges.
This is a list of material and conversion tables composed by the National Diet Library on the old calendars. There are clearly well-established method and researches about this. This would be the most basic problem for anyone studying history in Japan. It may be not straightforward (for you), but it certainly would be too generic and elementary for other historians to read in a paper like this.