Highcharts test tool

HTML

<script src="http://code.highcharts.com/stock/highstock.js"></script>
<div id="container" class="context-menu-one" style="height: 300px"></div>

JavaScript

var origData = {
    "2015-05-19T00:00:00": 20,
        "2015-05-20T00:00:00": 30,
        "2015-05-21T00:00:00": 50,
        "2015-06-21T00:00:00": 50,
        "2015-06-22T00:00:00": 50
};

// let's change to array format
var data = (function () {
    var d = [];
    for (var k in origData) {
        d.push([k, origData[k]]);
    }
    return d;
})();
var interval = 'Date'; //or Hour or Month or Year etc.

function fillData(data, interval) {
    var d = [],
        now = new Date(data[0][0]), // first x-point
        len = data.length,
        last = new Date(data[len - 1][0]), // last x-point
        iterator = 0,
        y;

    while (now <= last) { // loop over all items
        y = null;
        if (now.getTime() == new Date(data[iterator][0]).getTime()) { //compare times 
            y = data[iterator][1];
            iterator++;
        }
        d.push([now.getTime(), y]); // set point
        now["set" + interval](now.getDate() + 1); // jump to the next period
    }
    return d;
}

var chart = new Highcharts.StockChart({
    chart: {
        renderTo: 'container'
    },
    series: [{
        data: fillData(data, interval)
    }]
});