var monthName = new Array("January", 
						"February", 
						"March", 
						"April",
						"May", 
						"June", 
						"July", 
						"August", 
						"September", 
						"October",
						"November", 
						"December"); 

function clean_durationResult()
{
	document.durationCalculator.resultField.value="";
	document.durationCalculator.resultSum.value="";
}

function setCurrentDateA()
{
	var curDate = new Date();
	var curDay   = curDate.getDate();
	var curMonth = curDate.getMonth();
	var curYear  = curDate.getUTCFullYear();
	
	// set current day
	document.writeln("<select name=day_aField size=1 onchange=clean_durationResult()>");
	for (var i=1; i <= 31; i++) 
	{
		if (i == curDay)
			document.writeln("<option selected>" + i);
		else
			document.writeln("<option>" + i);
		
		document.writeln("</option>");
	}
	document.writeln("</select>");
	
	// set current month
	document.writeln("<select name=month_aField size=1 onchange=clean_durationResult()>");
	for (var j=0; j < 12; j++) 
	{
		if (j == curMonth)
			document.writeln("<option selected>" + monthName[j]);
		else 
			document.writeln("<option>" + monthName[j]);
			
		document.writeln("</option>");
	}
	document.writeln("</select>");
	
	// set current year
	document.writeln("<input type=text name=year_aField value="+ curYear + " size=4 maxlength=4 onkeypress=clean_durationResult()>");
}

function setCurrentDateB()
{
	var curDate = new Date();
	var curDay   = curDate.getDate();
	var curMonth = curDate.getMonth();
	var curYear  = curDate.getUTCFullYear();
	
	// set current day
	document.writeln("<select name=day_bField size=1 onchange=clean_durationResult()>");
	for (var i=1; i <= 31; i++) 
	{
		if (i == curDay)
			document.writeln("<option selected>" + i);
		else
			document.writeln("<option>" + i);
		
		document.writeln("</option>");
	}
	document.writeln("</select>");
	
	// set current month
	document.writeln("<select name=month_bField size=1 onchange=clean_durationResult()>");
	for (var j=0; j < 12; j++) 
	{
		if (j == curMonth)
			document.writeln("<option selected>" + monthName[j]);
		else 
			document.writeln("<option>" + monthName[j]);
			
		document.writeln("</option>");
	}
	document.writeln("</select>");
	
	// set current year
	document.writeln("<input type=text name=year_bField value="+ curYear + " size=4 maxlength=4 onkeypress=clean_durationResult()>");
}

function durationCalc(form)
{ 
	var a_day       = form.day_aField.selectedIndex + 1;
	var a_month     = form.month_aField.selectedIndex;
	var a_year      = form.year_aField.value;
	
	var b_day       = form.day_bField.selectedIndex + 1;
	var b_month     = form.month_bField.selectedIndex;
	var b_year      = form.year_bField.value;

	var _price      = form.costDay.value;
	price           = parseFloat(_price);
	
	clean_durationResult(); 
	int_aYear      = parseInt(a_year); 
	int_aMonth     = parseInt(a_month); 
	int_aDay       = parseInt(a_day); 
	
	int_bYear      = parseInt(b_year); 
	int_bMonth     = parseInt(b_month); 
	int_bDay       = parseInt(b_day); 
	
	int_aYear      = parseInt(a_year); 

	if ( (a_year == "") || !(int_aYear >= 1900) )
	{
		alert("Year must be an integer not less than 1900."); 
		document.durationCalculator.year_aField.focus(); 
		document.durationCalculator.year_aField.select(); 
		return false;
	}

	if ( (b_year == "") || !(int_bYear >= 1900) )
	{
		alert("Year must be an integer not less than 1900."); 
		document.durationCalculator.year_bField.focus(); 
		document.durationCalculator.year_bField.select(); 
		return false;
	}
	
	if ( ((int_aYear % 4)==0 && (int_aYear % 100)!=0) || (int_aYear % 400)==0 )
	{
		// leap year
		if ( ( int_aMonth == 1 ) && ( int_aDay > 29 ) )
		{ 
			alert("February cannot have more than 29 days in the leap year."); 
			return false;
		}
	}
	else
	{
		// nonleap year
		if ( ( int_aMonth == 1 ) && ( int_aDay > 28 ) )
		{ 
			alert("February cannot have more than 28 days."); 
			return false;
		}
	}
	
	if ( ((int_bYear % 4)==0 && (int_bYear % 100)!=0) || (int_bYear % 400)==0 )
	{
		// leap year
		if ( ( int_bMonth == 1 ) && ( int_bDay > 29 ) )
		{ 
			alert("February cannot have more than 29 days in the leap year."); 
			return false;
		}
	}
	else
	{
		// nonleap year
		if ( ( int_bMonth == 1 ) && ( int_bDay > 28 ) )
		{ 
			alert("February cannot have more than 28 days."); 
			return false;
		}
	}
	
	if ( ( (int_aMonth==3) || (int_aMonth==5) || (int_aMonth==8) || (int_aMonth==10) ) && (int_aDay>30) )
	{ 
		alert("This month cannot have more than 30 days."); 
		return false;
	}

	if ( ( (int_bMonth==3) || (int_bMonth==5) || (int_bMonth==8) || (int_bMonth==10) ) && (int_bDay>30) )
	{ 
		alert("This month cannot have more than 30 days."); 
		return false;
	}

	date_A = new Date(int_aYear, int_aMonth, int_aDay, 1, 1, 1);
	date_B = new Date(int_bYear, int_bMonth, int_bDay, 1, 1, 1);
	var day_step =  86400000;
	
	var days_count = Math.ceil( (date_B.getTime() - date_A.getTime()) / day_step );
	document.durationCalculator.resultField.value= days_count + " days";
	
	if ( (days_count == 0) || (price == 0) )
	{
		document.durationCalculator.resultSum.value= 0;
	}
	else
	{
		document.durationCalculator.resultSum.value= days_count * price;
	}
}