The file-system maintains a whole range of properties for its folders and files. This property exposes the date and time that the folder was last modified by adding files to it or removing them from it. It isn't clear whether modifying a file will affect the modification date and time of a folder that contains it. It may depend on the file-system the folder exists within and how the application modifies the file. It may rewrite the file and delete the old one. In that case, modifying a file will alter the modification date and time of the folder it lives in.