The value of "Clock Offset" isn't changed in virt-manager

0. Check the value of "clock offset" in a guest domain's xml file.
 # virsh edit <domain-name>
 ...
   <clock offset='utc'/>
 ...

 1. Run the virt-manager.
 2. Click the button "Show virtual hardware details" of a guest domain.
 3. Select another value of "Clock Offset" (e.g. localtime) in "Machine
    Settings" of Overview tab.
 4. Click the button "Apply".
 5. Check the value of "clock offset" in a guest domain's xml file.