Comment 5 for bug 963919

Same here. GNOME Classic under Ubuntu 12.10 – Indicator Applet Complete 12.10.1

Using dconf-editor, gconf-editor etc. has no effect on time format. In dconf-editor one can change to display date, seconds etc. but time format string has no effect.

This works: (Alt+F2 or in terminal)

    XDG_CURRENT_DESKTOP=Unity gnome-control-center indicator-datetime

Select clock and 24 hour format.

Alos note that adding the Clock item to panel does not have this bug. It is only for the one beside "Start" in upper right corner.