javascript 실시간 유동적 시간 변경

function getTime() {
  now = new Date();
  var montharray=new Array("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")
  var todayy=now.getYear();
  var todaym=now.getMonth();
  var todayd=now.getDate();
 
  var todaystring=montharray[todaym]+" "+todayd+", "+todayy+" 23:59:59";
 
  later = new Date(todaystring);
  days = (later - now) / 1000 / 60 / 60 / 24;
  daysRound = Math.floor(days);
  hours = (later - now) / 1000 / 60 / 60 - (24 * daysRound);
  hoursRound = Math.floor(hours);
  minutes = (later - now) / 1000 /60 - (24 * 60 * daysRound) - (60 * hoursRound);
  minutesRound = Math.floor(minutes);
  seconds = (later - now) / 1000 - (24 * 60 * 60 * daysRound) - (60 * 60 * hoursRound) - (60 * minutesRound);
  secondsRound = Math.round(seconds);
   
  if (secondsRound <= 9) {
   s1.innerHTML = "0";
   s2.innerHTML = secondsRound;
  } else {
   s1.innerHTML = Math.floor(secondsRound/10);
   s2.innerHTML = secondsRound%10;
  }
   
  if (minutesRound <= 9) {
   m1.innerHTML = "0";
   m2.innerHTML = minutesRound;
  } else {
   m1.innerHTML = Math.floor(minutesRound/10);
   m2.innerHTML = minutesRound%10;
  }
   
  if (hoursRound <= 9) {
   h1.innerHTML = "0";
   h2.innerHTML = hoursRound;
  } else {
   h1.innerHTML = Math.floor(hoursRound/10);
   h2.innerHTML = hoursRound%10;
  }
  newtime = window.setTimeout("getTime();", 1000);
 }
 function window::onload(){getTime();}