I cannot force clock in Gnome Classic to show seconds.
Tried within dconf-editor, changing all available clock settings:

com > canonical > indicatior > datetime
There I was trying by changing custom-time-format and setting time-format to custom and by checking show-seconds. Both does not work.

org > gnome > desktop > interface
I turned clock-show-seconds on. Nothing happened.

org > gnome > gnome-panel > shell > clock
show-seconds enabled, no reaction.

Also, I've been restarting system after each change.

Please, help - I need it for few things.

I'm using Ubuntu 12.04