In 14 RC . If you install gnome-system-tools and gnome-control-center packages via synaptic :
can't you access the gnome 'time applet' via the gnome volume control in the indicator applet on the panel ?
click volume control in the panel > sound settings > all settings > date and time
turn off network time and set the time/date/timezone you want then turn network time back on - and maybe reboot ?
ok i am using xfce 13 mint , this worked for me )) but got error saving gnome session , so i changed to xfce session and saved it as default this solved the time and zone setting issue thank you