Rules for "Date Modified" of folders in Windows Explorer

Disclaimer: I tested all of these myself on Windows 10. I could not find an authoritative source documenting all of these behaviours. It is entirely possible that I made a mistake somewhere.

The folder's last modified time is updated for these actions:

• new file or folder directly in target folder
• renamed file or folder directly in target folder
• deleted file or folder directly in target folder
• hardlink create/delete/rename - same as files
• file/folder symlink create/delete/rename
• directory junction create/delete/rename

It is not updated for these actions:

• modified contents of file directly in target folder
• edit target of symlink or junction contained in target folder
• file's or sub-folder's created/modified date changing
• edit basic attributes (hidden/archive/system) of a direct child
• NTFS compression/encryption change of a direct child
• anything at all happening in a sub-folder - literally anything
• changing attributes of the folder itself
• changing owner/ACL of the folder itself
• owner or ACL of a direct child changing
• if the folder is a directory junction, changing the target
• adding/deleting alt data streams to a direct child file

This is not explorer specific, this is NTFS-related.

See http://support.microsoft.com/kb/299648 https://web.archive.org/web/20080219020154/http://support.microsoft.com/kb/299648 for some rules.

Note: Modified time can be disabled with filesystem option, so you should never rely on it. Any suggested reliable methods would be appreciated.