Right ive had a play and here is how ya do it
With the stereo turned on to radio press the clk button to display clock (dont bother doing this if clock already displayed), now press and hold clk button for 5 seconds on releasing minutes should flash, each continous press of clk button will advance minutes by one. If you leave button alone for a few seconds it will then start the hours flashing and theese are changed by again pressing the clk button

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Good luck
Simon