Difference Between 2 Timestamps using javascript without using moment.js

-4 down vote favorite I have 2 timestamps var startTimestamp = 1488021704531; var endTimestamp = 1488022516572; I need the difference between these timestamps in hours and minutes using javascript but without using moment.js.

JavaScript

var startTimestamp = 1488021704531;
var endTimestamp = 1488022516572;
document.write(endTimestamp - startTimestamp + '<br/>');
document.write(millisecondsToHoursMinutesSeconds(endTimestamp - startTimestamp));

document.write('<hr/>');

function millisecondsToHoursMinutesSeconds(ms) {
    var milliseconds = parseInt((ms%1000)/100)
        , seconds = parseInt((ms/1000)%60)
        , minutes = parseInt((ms/(1000*60))%60)
        , hours = parseInt((ms/(1000*60*60))%24);

    hours = (hours < 10) ? "0" + hours : hours;
    minutes = (minutes < 10) ? "0" + minutes : minutes;
    seconds = (seconds < 10) ? "0" + seconds : seconds;

    return hours + ":" + minutes + ":" + seconds + "." + milliseconds;
}