I tried what was mentioned here to no avail. When I update the values in gconf (any of the values, not just custom and custom_format) nothing changes. Is this a netbook edition problem? Is there another clock that I should be looking for, where the changes actually are happening? I only see one clock in the panel. Thanks.
In 10.10 the tools have been changed to dconf. First install dconf-tools
sudo apt-get install dconf-tools
Then navigate to apps -> indicators -> datetime and then check the "show-date" checkbox.