There is currently an issue of files' last modified date being changed to the current date when transferred from laptop to the Android phone.
This is an Android project that attempts to allow user to select a WhatsApp image to fix the last modified date of that image.
The file.setLastModified() method is used in this project but apparently it has some issue changing the date. So this project has been left as-is. Until the issue has been fixed from Google's side.