Diplomat Select 620 S?

Hi there
We had a power cut and now I am unable to reset the clock. At present it reads 0:00 with 'AUTO' running down the left handside, sometimes the screen flashes and sometimes it doesn't. While the clock is not set my oven won't work.

There are six buttons on the screen, the last two are minus and plus buttons. I have tried pressing various combinations of these buttons, but cannot alter the digital screen display. I am due to host a dinner party tomorrow evening and am really quite desperate! Please can you help?