TimeSeries seriesOK =  new  TimeSeries("OK",Hour. class );
    ... заполнение seriesOK
   TimeSeriesCollection dataset =  new  TimeSeriesCollection();
   dataset.addSeries(series1);
   JFreeChart chart = ChartFactory.createTimeSeriesChart(
                    "Any Title",
                    "Date", "Value",
                    dataset,
                    true,
                    true,
                    false
                    );
    XYPlot plot = chart.getXYPlot();
    DateAxis axis = (DateAxis) plot.getDomainAxis();
    axis.setDateFormatOverride( new  SimpleDateFormat("dd.MM.yy HH"));