tar and --newer usage?

[Scott R. Ehrlich]

I have a RHEL 5.0 Server and CentOS 5.0 machine, both out-of-box installs, 
including all packages from CDs.

I have discovered that tar with the --newer option only seems to correctly 
perform the "diff" of newer files when it runs on the server housing the 
data (RHEL 5.0 in this case).   If I run it on exported directories (on 
the CentOS 5.0 system), all files are archived (i.e. --newer doesn't 
seem to do anything).

The exports are via CIFS.   Would it make any difference if the export was 
via NFS?

Is this the way tar --newer/--after-date/-N should work?  Just on the 
server housing the data?

I use tar because it is the most reliable archive method that can be used 
with Linux out of the box, no database is needed (such as with bacula, 
etc), and it is free.

Thanks for any insights and feedback.

Scott