private void stepMinute() {
    if(fIsPlus){
      fMinute = fMinute + 1;      
    }
    else {
      fMinute = fMinute - 1;      
    }
    if(fMinute > 59){
      fMinute = 0;
      stepHour();
    }
    else if (fMinute < 0){
      fMinute = 59;
      stepHour();
    }
  }