<script LANGUAGE="JavaScript">
//澳门回归倒计时代码
var Temp;
var timerID = null;
var timerRunning = false;
function showtime() {
now = new Date();
var CurHour = now.getHours();
var CurMinute = now.getMinutes();
var CurSecond = now.getSeconds();
var now1=now.getTime();
var ts=parseInt((945619200000-now.getTime())/1000);
var Dateleft =parseInt(ts/86400);
//每天24小时，共86400秒
now = null;
Hourleft = 23 - CurHour
Minuteleft = 59 - CurMinute
Secondleft = 59 - CurSecond
if (Dateleft!=1) {var ds="s"} else {var ds=""}
if (Hourleft!=1) {var hs="s"} else {var hs=""}
if (Minuteleft!=1) {var mis="s"} else {var mis=""}
if (Secondleft!=1) {var ss="s"} else {var ss=""}
Temp=Dateleft+"天"+Hourleft+"小时"+Minuteleft+"分钟"+Secondleft+"秒。"
document.frm.left.value=Temp;
timerID = setTimeout("showtime()",1000);
timerRunning = true;
}
var timerID = null;
var timerRunning = false;
function stopclock() {
if(timerRunning)
clearTimeout(timerID);
timerRunning = false;
}
function macauclock() {
stopclock();
showtime();
}
</script>
<body Onload="macauclock()">
<table border="1" width="100%">
<tr>
<td width="100%"><font color="#008000">距</font><font color="#FF0000">1999年12月20日</font>
<font color="#008000">澳门回归祖国还有</font></td>
</tr>
<tr>
<td width="100%">
<form name="frm">
<div align="center"  align="middle">
<div align="center"><center><p><input type="textarea" name="left"  size="22"  value=""></p>
</center></div></div>
</form>
</td></tr></table>
</body>
====================================================
问：
以上代码中
var ts=parseInt((945619200000-now.getTime())/1000);
其中945619200000是怎么计算的？？？？