For brush calligraphy, the traditional format is generally used. Signature can have a deposit. Common only the next paragraph, the format is:
Time (usually not Gregorian calendar)+(%location)+author+(respect) book
Such as: "Gengzi Qiuyue worships books in Gufengtang XX".
In traditional calligraphy, dates are marked by years, and months are marked by lunar calendar, not specific to a certain day.
Hard-pen calligraphy, if arranged horizontally, can be in a modern format: XXX books on X month X day in 2020. If it is vertical, it should also be in the traditional format.