tell the system hardware clock is localtime

[Rakotomandimby Mihamina]

Hi,
On my latptop, I changed the hardware time to localtime, for a precise 
reason. Before, the hardware time was UTC and my timezone was GMT+2.

Now, I want to tell the system to display the right time (the hardware 
time, which is the localtime).
Reconfiguring tzdata doesn't help as well as there is no "hardware clock 
is in local time" option.

I use Xubuntu, with XFCE environment.

How to configure my system so that it knows that hardware time is localtime?

Thank you.