function refreshTimer(){
function countDown(){
setTimeout(function(now){
var dif = (td-now)/1000,
ss = Math.floor(dif % 60).toString().padStart(2,"0"),
ms = Math.floor(dif/60 % 60).toString().padStart(2,"0"),
hs = Math.floor(dif/3600 % 24).toString().padStart(2,"0"),
ds = Math.floor(dif/86400).toString().padStart(3,"0");
remainingTime.textContent = dif > 0 ? `${ds} Days ${hs}:${ms}:${ss}`
: "Sorry. You are already late..!";
active && countDown();
this.removeEventListener("change", kill); // possibly redundant
}, 1000, Date.now());
}
var td = new Date(this.value),
active = true,
kill = _ => active = false;
this.addEventListener("change", kill);
countDown();
}
var targetDateTime = document.getElementById("targetDateTime"),
remainingTime = document.getElementById("remainingTime");
targetDateTime.addEventListener("change",refreshTimer);