Highcharts Gantt Chart

HTML

<script src="http://code.highcharts.com/stock/highstock.js"></script>
<div id="container" style="height: 500px"></div>

JavaScript

Date.prototype.addMinutes = function(minutes) {
    var copiedDate = new Date(this.getTime());
    return new Date(copiedDate.getTime() + minutes * 60000);
};


$(function () {
		   	// Define tasks
		   	var tasks = [{
		   	    name: '',
		   	    intervals: [{ // From-To pairs
		   	        from: new Date('2018-12-13 13:12:27.000').addMinutes(60),
		   	        to: new Date('2018-12-13 13:16:01.000' ).addMinutes(60),
		   	        label: 'Praca'
		   	    }, {
		   	        from: new Date('2018-12-13 13:04:41.000').addMinutes(60),
		   	        to: new Date('2018-12-13 13:08:28.000').addMinutes(60),
		   	        label: 'Praca'
		   	    }]
		   	}];

		   	var series = [];
		   	$.each(tasks.reverse(), function(i, task) {
		   	    var item = {
		   	        name: task.name,
		   	        data: []
		   	    };
		   	    $.each(task.intervals, function(j, interval) {
		   	        item.data.push({
		   	            x: interval.from,
		   	            y: i,
		   	            label: interval.label,
		   	            from: interval.from,
		   	            to: interval.to
		   	        }, {
		   	            x: interval.to,
		   	            y: i,
		   	            from: interval.from,
		   	            to: interval.to
		   	        });
		   	        
		   	        // add a null value between intervals
		   	        if (task.intervals[j + 1]) {
		   	            item.data.push(
		   	                [(interval.to + task.intervals[j + 1].from) / 2, null]
		   	            );
		   	        }

		   	    });

		   	    series.push(item);
		   	});


		   	var chart = new Highcharts.Chart({
		   	    chart: {
		   	        renderTo: 'container'
		   	    },

		   	    title: {
		   	        text: 'Czas Pracy'
		   	    },

		   	    xAxis: {
		   	        type: 'datetime'
		   	    },

		   	    yAxis: {

		            categories: ['Praca',
		                         'Category 1'],
		   	        tickInterval: 1,            
		   	        tickPixelInterval: 200,
		   	 ...