Whenever you edit or create a file that is placed inside a folder, even though the creation date and modification date attributes of the file itself are set correctly, but the folder that contains it has the date of creation/modification of the folder rather than the files contained in it. That is the behavior of files on both Windows as well as Mac OS X.
The problem with this setup is that in folders that contain a large number of files, which are edited regularly, there is no way of knowing whether a contained file inside it has been recently edited or not, other than opening up the folder and checking manually each file for its last date of modification or creation. When working with large data sets, this can become tedious.
For Mac OS X, there exists a freeware application called SyncFF which automates this tedious job for you. It can scan folders for contained files (or optionally, folders) and their created and last modified date. Then, it sets the created and last modified date of the parent folder to the most recent contained file/folder attributes. It can also do this recursively.
To sync a particular folder, you can launch the SyncFF application, and drop the folder onto it. SyncFF will handle the rest. Alternatively, you may also use the ‘Services’ tab in the context menu of any folder to perform this action. It is highlighted in the screenshot below:
You can also set a global hotkey to invoke this action on the selected folder using the System Preferences.
Once SyncFF is done with its processing, it records all the changes made by it to a log file, which can viewed by visiting the ‘File’ menu from SyncFF. You may also choose to ignore folders while doing the changes, and may set other useful options from the preferences menu of SyncFF.