anchor.diff:    end;
   end;
   
  -procedure TSantosLayer.UpdateStopsOnTime(aTime: TDateTime);
  +function TSantosLayer.UpdateStopsOnTime(aTime: TDateTime): TDateTime;
   var
     ttt: TArray<TDateTime>;
  -  sliderTime: TDateTime;
  +  //sliderTime: TDateTime;
     t: Integer;
     sl: TSliderRecord;
     ibsp: TPair<string, TBusStop2>;
  
positive.code:     if length(ttt)>0 then
      begin
        // find time on or below slider time
        sliderTime := ttt[0]; // sentinel: lowest value
        for t := length(ttt)-1  downto 0 do
        begin
          if ttt[t]<=aTime then
          begin
            sliderTime := ttt[t];
            break;
          end;
        end;
        // process data on slider time
        if fSliderData.TimeTable.TryGetValue(sliderTime, sl) then
        begin
          for ibsp in fSliderData.BusStops do
          begin
  
negative.code:   bdes: TBusTimeTable;
    at: TDateTime;
    curDate: TDateTime;
    bde: TBusDataEntry;
  begin
    TMonitor.Enter(fBusData);
    try
  