เราจะลบวันที่แล้วให้แสดงจำนวนวัน ด้วย Javascript อย่างไร...JavaScript DateDiff , JavaScript TimeDiff

<script language="javascript">
	StratDate = new Date( );          
	EndDate = new Date( );      

	StratDate.setDate(12);					//กำหนดวันเริ่มต้น	
	StratDate.setMonth(30);				//กำหนดเดือนเริ่มต้น
	StratDate.setFullYear( 2009);	//กำหนดปีเริ่มต้น

	EndDate.setDate(15);					//กำหนดวันสิ้นสุด
	EndDate.setMonth(11);				//กำหนดเดือนสิ้นสุด
	EndDate.setFullYear( 2009)		//กำหนุดปีสิ้นสุด
			
	if (StratDate.getTime( ) < EndDate.getTime( ))
	 {  
		diff = EndDate.getTime( ) - StratDate.getTime( );	//วันสุดท้าย - วันเริ่ม = ? millisec
		diff = Math.floor(diff / (1000 * 60 * 60 * 24));					
		var strdiff = document.write(diff + ' days ');
		alert(strdiff);
	  }
</script>

<SCRIPT language="javascript">
function TimeDriff()
{
	var diff;
	var start = new Array(3);
	var end = new Array(3);
	var st = document.getElementById('start').value;
	var en = document.getElementById('end').value;

	//Thai DateFormat 15/08/2552 - DD/MM/YYYY
	
	//Split Start -> Date/Month/Year
	start[0] = st.substr(0,2);
	start[1] = st.substr(3,2);
	start[2] = st.substr(6,4);
		
	//Split End -> Date/Month/Year
	end[0] = en.substr(0,2);
	end[1] = en.substr(3,2);
	end[2] = en.substr(6,4);

	end[1] -= 1;
	start[1] -= 1;

	end[2] -= 543;
	start[2] -= 543;  

	StratDate = new Date( );          
	EndDate = new Date( );     

	StratDate.setDate(start[0]);					
	StratDate.setMonth(start[1]);				
	StratDate.setFullYear(start[2]);	

	EndDate.setDate(end[0]);					
	EndDate.setMonth(end[1]);				
	EndDate.setFullYear(end[2])		
	
	if(StratDate.getTime( ) < EndDate.getTime( ))
	{  
		diff = EndDate.getTime( ) - StratDate.getTime( );
		diff = Math.floor(diff / (1000 * 60 * 60 * 24));
	 }
	else if(EndDate.getTime( ) < StratDate.getTime( ))
	{
		diff = "0";
	}
	else if(EndDate.getTime( ) == StratDate.getTime( ))
	{
		diff = "0";
	}

	if(diff==undefined)
		document.getElementById("tmdiff").value = "";
	else
		document.getElementById("tmdiff").value = diff;
}

</SCRIPT>
<b>Calculate Time Between </b><p>
<table border="1" cellspacing="0" cellpadding="2">
<tr><td>Time Start : </td><td><input type="text" id="start" name="start" onChange="TimeDriff()"></td></tr>
<tr><td>Time End : </td><td><input type="text" id="end" name="end" onChange="TimeDriff()"></td></tr>
<tr><td>Time Diff : </td><td><input type="text" id="tmdiff" name="diff"> Days</td></tr>
</table>

/**
 * convert string date to date object
 */
var stringToDateObject = function(stringDate) {
	var arrString = stringDate.split("/");
	return new Date(arrString[1] + "/" + arrString[0] + "/" + arrString[2]);
};

/**
 * calculate date between of two dates
 */
var dateBetween = function(startDate , endDate) {
	var sDate = stringToDateObject(startDate);
	var eDate = stringToDateObject(endDate);
	// convert 1 day to milisecound	
	var oneDay = 24 * 60 * 60 * 1000;
	
	return Math.round((eDate.getTime() - sDate.getTime()) / oneDay);
};

/**
 * input date format  dd/mm/yy
 * javascrip date fomat  mm/dd/yys
 */
alert("date between: " + dateBetween("01/02/2010", "01/01/2011"));