The modified timestamps are not updated when documents are added to folders or move between folders. This is the case even when the NotesDatabase.FolderRefsEnabled property is true and moving the document between folders causes the $FolderRef, $FolderRefID and $FolderRefFlags to be updated.
I am trying to use the timestamps to optimize processing by skipping unmodified databases and documents based on the timestamp. However, if the timestamp is not reliably updated this will not work.
In Notes, a document is modified, and thus the timestamp updated, if a substantive change to the document occurs. Changing the location of a document within a user's filing system is not a substantive change to the Note itself, but simply a user's preference as to which "places" the Note should appear within the database, thus the Note's timestamp is not modified.
This was first published in June 2005