Getting time offset to server javascript

function getTimeDifferenceSynchronous(){
    timings = [];
    // Time synchronization
    for(var i = 0; i < 16; i++) {
        timings[i]=Date.now()/1000;
        var result = $.ajax("/api.php", {
            type: "GET",
            async: false,
            data: {
                type: "get_time",
            }
        }).responseText;
        timings[i] = ((timings[i]+(Date.now()/1000))/2) - result;
    }


    // Analyze time sync data
    timings.sort();
    iqr = timings[12]-timings[4];
    count = 0;
    mean = 0;
    for(i=0; i < 16; i++) {
        if (timings[i] > (timings[8] - 1.5*iqr) && timings[i] < (timings[8] + 1.5*iqr)) {
            count++;
            mean += timings[i];
        }

    }

    mean = mean/count;
    return mean;
}

// PHP CODE: Returns time in 'seconds.microseconds' format.
<?php
if (!empty($_GET['type'] && $_GET['type'] == 'get_time') echo microtime(true);