How to Reset the clock on a citroen c3?

You need to use both the buttons on the display screen. First press the left button and keep it press till display flashes. Then short presses to select the parameters you wish to change.

Use the right button to adjust the parameter selected.

A long press on the right button scrolls down the possible values. Press the left button to store the value before going to the next parameter.

To adjust time display press the left button to change the hours and the right button to change the minutes.