If your radio controlled clock tells the wrong time, it may be because:

• The signal from the National Physics Laboratory (NPL) is low and your clock is finding it difficult to recieve the signal. Repositioning your clock may solve this issue.
• Every hour your clock will check the time with NPL - there may be an outage which is stopping the time being transmitted. You can check this here: http://www.npl.co.uk/time/msf/msfoutages.html

If you hit the red reset button at the back of your clock, it should go through its set up routine again and get the correct time.