this paragraph is the countdown code, what does he mean? 
 function checkTime (i) 
{
    if(i<10)
    {
        i="0"+i;
    }
    return i;
}
var time = setInterval("showTime()",500);
function showTime()
{
  var timedate= new Date("2018/12/01,10:13:55");                  
var now = new Date();                                         
var date = parseInt(timedate.getTime() - now.getTime())/1000; 
  if(date <= 0)
  {
      document.getElementById("txtshow").innerHTML="";
      clearInterval(time);
  }
var day = parseInt(date/60/60/24);     
    var hour = parseInt(date/60/60%24);
    var minute = parseInt(date/60%60);
    var second = parseInt(date%60);
    hour = checkTime(hour);
    minute = checkTime(minute);
    second = checkTime(second);
    var leftTime = day+""+hour+""+minute+""+second+"";
    document.getElementById("timeShow").innerHTML = leftTime;
    time;        
						