I need JavaScript code to calculate date difference

I want to calculate the months, days, hours and seconds from a specified date. For example from 2018/09/09 I need output as one year, 3 months, 20 days and 10 hours and something seconds and still counts on itself in future.

I tried using this code but this couldn't help.

var timerVar = setInterval(countTimer, 1000);
var totalSeconds = 0;
function countTimer() {
   ++totalSeconds;
   var hour = Math.floor(totalSeconds /3600);
   var minute = Math.floor((totalSeconds - hour*3600)/60);
   var seconds = totalSeconds - (hour*3600 + minute*60);
   if(hour < 10)
     hour = "0"+hour;
   if(minute < 10)
     minute = "0"+minute;
   if(seconds < 10)
     seconds = "0"+seconds;
   document.getElementById("timer").innerHTML = hour + ":" + minute + ":" + seconds;
}