gnome-tweak-tool to change Gnome 3 Settings

[Updated 2013-06-20]

You can modify the gnome settings using gnome-tweak-tool

E.g. The clock/date settings
If you want to show the date in the clock on the top bar:

1. Launch the gnome-tweak-tool
2. Go to the "Shell" menu
3. Enable "Show date in clock"