dateformatter - Formatting Highchart dateime time categories -

can please tell me how specify format categories in following code. why xaxis categories in milliseconds getting converted "1970-01-01 00:00:00"

here link fiddler

var chart = new highcharts.chart({      chart: {         renderto: 'container'     },      title: {         text: 'categorized chart'     },      xaxis: {         categories: [1496275200000,1498867200000,1501545600000,1504224000000],         type : 'datetime'     },      series: [{         data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]     }]  });  $('#preview').html(chart.getcsv()); 

take idea official example

your code

xaxis: {     //categories: [1496275200000,1498867200000,1501545600000,1504224000000],     type : 'datetime' },  series: [{     data: [[1496275200000,29.9],[1498867200000,71.5],[1501545600000,106.4] , [1504224000000,129.2]] }] 

fiddle demo