My code does not show in the x axis the timestamp data in the firebase

My code does not show in the x axis the timestamp data in the firebase
Instead of showing the timestamp in the firebase which is 11:27:47, it shows 8:00:00

This is my code in array:

if (is_array($data)) {
    foreach ($data as $user) {
        $dataPointsx[] = array("x" => $user['Timestamp'], "y" => $user['Luminosity']);
        array_push($dataPointsy, array("y" => $user['Luminosity']));
    }
}

While this is the graph:

window.onload = function() {


var dataPointsy= <?php echo json_encode($dataPointsy); ?>;
var dataPointsx= <?php echo json_encode($dataPointsx); ?>;
 
var chart = new CanvasJS.Chart("chartContainer", {
    animationEnabled: true,
    theme: "light2",
    title: {
        text: "Luminosity"
    },
    axisX:{
    title: "Timestamp",
    valueFormatString: "HH:mm:ss",
    labelFormatter: function(e){
        return new Date(e.value).toLocaleTimeString();

    },
    interval: 1
},
    axisY:{

        suffix: " Luminosity"
    },
    data: [{
    type: "line",
    toolTipContent: "{y} L⊙ {x}",
    dataPoints: dataPointsy,
}]
});
chart.render();
}