[Samba] Archive bit not changed if not owner?

[John Perazo]

We have a public share which is backed up from another machine, and use
the archive bits to detect if files have been modified.

If I create a file in the public share, the archive bit is set.

If I clear the archive bit, and then modify the file the archive bit is set.

On the other hand, if I modify a file that is owned by someone else, the
archive bit doesn't get set - any ideas on why this is?

Here's a snippet from smb.conf:

[shared]
    comment = Shared stuff
    path = /data/shared
    public = yes
    create mask = 0774
    force create mode = 0777
    directory mask = 0700
    force directory mode = 0775

    #allow anyone to change the archive bit
    dos filemode = yes