Annotated calendar for the 4th year of Ōei (1397-1398) (應永四年具注暦). From: Digital Collection of National Diet Library Tokyo. https://dl.ndl.go.jp/info:ndljp/pid/2585025
Geographical names, forms, and borders are not permanent. They are rather amorphous and change over time. Thus, reading a historical map not only requires to grasp the geo-spatial information, but also to detect the chronological information - in which time was the spatial description of a map valid?
In this exercise, we will explore the chronological information contained in two different maps. You should only find their publication dates. They point at the possible period of validity of the maps.
You will soon see that the chronological information in the maps differs from the western convention. It is written in Japanese, and it follows another calendar system. The Japanese calendar converter is useful for this purpose.
Kamiya Nobutake, Ad fontes, Dating Maps, URL: www.adfontes.uzh.ch/382100