JSFiddle - React, Tailwind, and code Playground

HTML

<div id="millisecDiv">Milliseconds:</div>
<div id="check">Actual date:</div>
<br />
<div id="result">Result: </div>

JavaScript

//get current date in milliseconds:
var millisec = new Date(108120000); 

//show it:
var millisecDiv = document.getElementById("millisecDiv");
millisecDiv.innerHTML += millisec;

//make sure it is the correct date
var check = document.getElementById("check");
check.innerHTML += new Date(millisec);

//and the answer to the question:
var dtFromMillisec = new Date(millisec);
var res = document.getElementById("result");
res.innerHTML += dtFromMillisec.getHours() + ":" + dtFromMillisec.getMinutes() + ":" + dtFromMillisec.getSeconds() + "." + millisec % 1000;