Please note that many of the functions below that people have provided to get files modified after a certain time in a directory will NOT get all files on a Windows operating system.
If you copy and paste any file inside the folder or into the folder from another folder (such as images that may be used but aren't going to be modified right away), the modified time is not updated on these copied files, only the creation time.
You need to use filectime with filemtime to assure you get copied files that aren't modified but are obviously new.