Permissions have me stumped

[Kirk Strauser]

I have a directory, /usr/share/media, where I store all my pictures, songs,
videos, and other random stuff.  The directory is chgrp media and chmod
2770 so that every member of the media group can write to it, and all files
writing to it will be readable by everyone else in the media group.

What I don't really understand is why I can't update any timestamps on its
subdirectories, even though it looks like I should be able to:

    $ ls -lad /usr/share/media/music
    drwxrws---  4 root  media  512 Mar  1 14:40 /usr/share/media/music
    $ touch -t 200603011234.45 /usr/share/media/music
    touch: /usr/share/media/music: Operation not permitted

The only reason this is an issue at all is that I have a script that rsyncs
my this directory tree with a similar one on my machine at work, and it
throws a large number of warnings ever time the rsync command runs:

    $ rsync -auvx janus:/usr/share/media/music/ /usr/share/media/music/
    receiving file list ... done
    rsync: failed to set times on "/usr/share/media/music/.": Operation not permitted (1)
    rsync: failed to set times on "/usr/share/media/music/albums": Operation not permitted (1)
    rsync: failed to set times on "/usr/share/media/music/singles": Operation not permitted (1)
    rsync: failed to set times on "/usr/share/media/music/.": Operation not permitted (1)
    rsync: failed to set times on "/usr/share/media/music/albums": Operation not permitted (1)
    rsync: failed to set times on "/usr/share/media/music/singles": Operation not permitted (1)
    ...

I know this is pretty minor in the scheme of things, but it still bothers me
because it looks like it should work, but it doesn't.
-- 
Kirk Strauser