Highcharts timeseries not correct plotted - highcharts

Question

Trying to get data from a backing bean to a Highchart line chart.
Problem is, that i need a timeseries with a datetime format, but Java cannot create a JS Date Object. Even with milliseonds, the chart won't display the date.
Sample code of the backing bean:
final List<LineChartSeries> series = new ArrayList<>();
final LineChartSeries chartSerie = new LineChartSeries();
final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
LineSeries2 lineSeries = new LineSeries2();
lineSeries.setY(0.654);
lineSeries.setDate(sdf.parse("2016-01-01").getTime());
chartSerie.addData(lineSeries);
lineSeries = new LineSeries2();
lineSeries.setY(0.337);
lineSeries.setDate(sdf.parse("2016-02-01").getTime());
chartSerie.addData(lineSeries);
lineSeries = new LineSeries2();
lineSeries.setY(0.547);
lineSeries.setDate(sdf.parse("2016-03-01").getTime());
chartSerie.addData(lineSeries);
series.add(chartSerie);
chartData = new Gson().toJson(series);
which produces a JSON like
[{"data":[{"date":1451602800000,"y":0.654},{"date":1454281200000,"y":0.337},{"date":1456786800000,"y":0.547}]}]
My JSF Page with the Highchart (part of)
<script type="text/javascript">
$(function () {
$('#ctrContainer').highcharts({
chart : {
zoomType: 'x'
},
title : {
text : 'VTR'
},
xAxis: {
type: 'datetime'
},
yAxis: {
title: {
text: 'Exchange rate'
}
},
legend: {
enabled: false
},
plotOptions: {
area: {
fillColor: {
linearGradient: {
x1: 0,
y1: 0,
x2: 0,
y2: 1
},
stops: [
[0, Highcharts.getOptions().colors[0]],
[1, Highcharts.Color(Highcharts.getOptions().colors[0]).setOpacity(0).get('rgba')]
]
},
marker: {
radius: 2
},
lineWidth: 1,
states: {
hover: {
lineWidth: 1
}
},
threshold: null
}
},
credits: {
enabled: false
},
series : $.parseJSON('#{lineChartController.chartData}')
});
The data for y-axis will be plotted correctly, but the "date" data are not correct interpreted. Any suggetions?