DateAxis axis = (DateAxis) xyPlot.getDomainAxis();
axis.setRange(_model.getStartDate(), _model.getEndDate());
axis.setLabel(_getXAxisLabel());
// mark the ranges of twilight and darkness
xyPlot.clearDomainMarkers();
_addDarknessMarker(xyPlot, _model.getNauticalTwilightStart(),
_model.getNauticalTwilightEnd(), TWILIGHT_ALPHA, Color.gray);
_addDarknessMarker(xyPlot, _model.getAstronomicalTwilightStart(),
_model.getAstronomicalTwilightEnd(), DARKNESS_ALPHA, Color.black);
}