High Precision Clock

HTML

<p><span id="clock">00:00:00</span></p>

CSS

#clock {
    font-family: monospace;
    font-weight: bold;
    padding: 10px;
}

JavaScript

var clockElement = document.getElementById("clock");

var countDownDate = new Date("Sep 5, 2018 15:37:25").getTime();

function updateClock() {
    var d = new Date();

    var h = d.getHours();
    var m = d.getMinutes();
    var s = d.getSeconds();

    h = (h < 10 ? "0" : "") + h;
    m = (m < 10 ? "0" : "") + m;
    s = (s < 10 ? "0" : "") + s;

    clockElement.innerHTML = h + ":" + m + ":" + s;
    $(clockElement).effect("highlight", {}, 800);

    msUntilNextSecond = (1000 - (new Date().getTime() % 1000));

    setTimeout(updateClock, msUntilNextSecond);
}

updateClock();