Japan traditionally used the lunisolar calendar - so if any record says "blossoms peaked at the fifth day of the fourth month," then it means it peaked at the f

Japan traditionally used the lunisolar calendar - so if any record says "blossoms peaked at the fifth day of the fourth month," then it means it peaked at the fifth day after some day of the new moon, which can be calculated with very good precision. It should severely constrain potential calendar conversion errors.