为什么我输出的是NAN。 帮忙给看下，在线等
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>高考时间倒计时</title>
<script language="JavaScript" type="text/javascript">
window.onload = function(){
var curtime = new Date();
var endtime = new Date("2018,6,6");
var lefttime = Math.ceil((endtime.getTime() - curtime.getTime()) / (24*60*60*1000));
document.getElementById('timeshow').innerHTML =lefttime;
}
</script>
</head>
<body>
<div class="content2">
<div class="textshow">高考还有：<span id="timeshow"></span>天</div>
</div>
</body>
</html>
