//------------------------ date validation------------------------------------------- 
var dtCh= "/";
	var minYear=1900;
	var maxYear=2100;

	function isInteger(s){
		var i;
	    for (i = 0; i < s.length; i++){   
	        // Check that current character is number.
	        var c = s.charAt(i);
	        if (((c < "0") || (c > "9"))) return false;
	    }
	    // All characters are numbers.
	    return true;
	}
	
	function stripCharsInBag(s, bag){
		var i;
	    var returnString = "";
	    // Search through string's characters one by one.
	    // If character is not in bag, append to returnString.
	    for (i = 0; i < s.length; i++){   
	        var c = s.charAt(i);
	        if (bag.indexOf(c) == -1) returnString += c;
	    }
	    return returnString;
	}
	
	function daysInFebruary (year){
		// February has 29 days in any year evenly divisible by four,
	    // EXCEPT for centurial years which are not also divisible by 400.
	    return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
	}
	function DaysArray(n) {
		for (var i = 1; i <= n; i++) {
			this[i] = 31
			if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}
			if (i==2) {this[i] = 29}
	   } 
	   return this
	}
	
	function isDate(dtStr){
		var daysInMonth = DaysArray(12)
		var pos1=dtStr.indexOf(dtCh)
		var pos2=dtStr.indexOf(dtCh,pos1+1)
		var strDay=	dtStr.substring(0,pos1)
		var strMonth=dtStr.substring(pos1+1,pos2)
		var strYear=dtStr.substring(pos2+1)
		strYr=strYear
		if (strDay.charAt(0)=="0" && strDay.length>1) strDay=strDay.substring(1)
		if (strMonth.charAt(0)=="0" && strMonth.length>1) strMonth=strMonth.substring(1)
		for (var i = 1; i <= 3; i++) {
			if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1)
		}
		month=parseInt(strMonth)
		day=parseInt(strDay)
		year=parseInt(strYr)
		if (pos2==-1 || pos1==-1){
			alert("The date format should be : dd/mm/yyyy")
			return false
		}
		if (strMonth.length<1 || month<1 || month>12){
			alert("Please enter a valid month")
			return false
		}
		if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month]){
			alert("Please enter a valid day")
			return false
		}
		if (strYear.length != 4 || year==0 || year<minYear || year>maxYear){
			alert("Please enter a valid 4 digit year between "+minYear+" and "+maxYear)
			return false
		}
		if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false){
			alert("Please enter a valid date")
			return false
		}
	return true
	}
//------------------------------------------------------------------- 
// Author: Denis Gritcyuk <denis@softcomplex.com>; <tspicker@yahoo.com>
function show_calendar(str_target, str_datetime) {
	var arr_months = ["January", "February", "March", "April", "May", "June",
		"July", "August", "September", "October", "November", "December"];
	var week_days = ["Su", "Mo", "Tu", "We", "Th", "Fr", "Sa"];
	var n_weekstart = 1; // day week starts from (normally 0 or 1)

	var dt_datetime = (str_datetime == null || str_datetime =="" ?  new Date() : str2dt(str_datetime));
	var dt_prev_month = new Date(dt_datetime);
	dt_prev_month.setMonth(dt_datetime.getMonth()-1);
	var dt_next_month = new Date(dt_datetime);
	dt_next_month.setMonth(dt_datetime.getMonth()+1);
	var dt_firstday = new Date(dt_datetime);
	dt_firstday.setDate(1);
	dt_firstday.setDate(1-(7+dt_firstday.getDay()-n_weekstart)%7);
	var dt_lastday = new Date(dt_next_month);
	dt_lastday.setDate(0);
	
	// html generation (feel free to tune it for your particular application)
	// print calendar header
	var str_buffer = new String (
		"<html>\n"+
		"<head>\n"+
		"	<title>Calendar</title>\n"+
		"</head>\n"+
		"<body bgcolor=\"White\">\n"+
		"<table class=\"clsOTable\" cellspacing=\"0\" border=\"0\" width=\"100%\">\n"+
		"<tr><td bgcolor=\"#336699\">\n"+
		"<table cellspacing=\"1\" cellpadding=\"3\" border=\"0\" width=\"100%\">\n"+
		"<tr>\n	<td bgcolor=\"#336699\"><a href=\"javascript:window.opener.show_calendar('"+
		str_target+"', '"+ dt2dtstr(dt_prev_month)+"'+document.cal.time.value);\">"+
		"<img src=\"images/cal_prev.gif\" width=\"13\" height=\"13\" border=\"0\""+
		" alt=\"previous month\"></a></td>\n"+
		"	<td bgcolor=\"#336699\" colspan=\"5\">"+
		"<font color=\"white\" face=\"tahoma, verdana\" size=\"2\">"
		+arr_months[dt_datetime.getMonth()]+" "+dt_datetime.getFullYear()+"</font></td>\n"+
		"	<td bgcolor=\"#336699\" align=\"right\"><a href=\"javascript:window.opener.show_calendar('"
		+str_target+"', '"+dt2dtstr(dt_next_month)+"'+document.cal.time.value);\">"+
		"<img src=\"images/cal_next.gif\" width=\"13\" height=\"13\" border=\"0\""+
		" alt=\"next month\"></a></td>\n</tr>\n"
	);

	var dt_current_day = new Date(dt_firstday);
	// print weekdays titles
	str_buffer += "<tr>\n";
	for (var n=0; n<7; n++)
		str_buffer += "	<td bgcolor=\"#66CCFF\">"+
		"<font color=\"black\" face=\"tahoma, verdana\" size=\"2\">"+
		week_days[(n_weekstart+n)%7]+"</font></td>\n";
	// print calendar table
	str_buffer += "</tr>\n";
	while (dt_current_day.getMonth() == dt_datetime.getMonth() ||
		dt_current_day.getMonth() == dt_firstday.getMonth()) {
		// print row heder
		str_buffer += "<tr>\n";
		for (var n_current_wday=0; n_current_wday<7; n_current_wday++) {
				if (dt_current_day.getDate() == dt_datetime.getDate() &&
					dt_current_day.getMonth() == dt_datetime.getMonth())
					// print current date
					str_buffer += "	<td bgcolor=\"#66CCFF\" align=\"right\">";
				else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6)
					// weekend days
					str_buffer += "	<td bgcolor=\"#EFEFEF\" align=\"right\">";
				else
					// print working days of current month
					str_buffer += "	<td bgcolor=\"white\" align=\"right\">";

				if (dt_current_day.getMonth() == dt_datetime.getMonth())
					// print days of current month
					str_buffer += "<a href=\"javascript:window.opener."+str_target+
					".value='"+dt2dtstr(dt_current_day)+"'+document.cal.time.value; window.close();\">"+
					"<font color=\"black\" face=\"tahoma, verdana\" size=\"2\">";
				else 
					// print days of other months
					str_buffer += "<a href=\"javascript:window.opener."+str_target+
					".value='"+dt2dtstr(dt_current_day)+"'+document.cal.time.value; window.close();\">"+
					"<font color=\"gray\" face=\"tahoma, verdana\" size=\"2\">";
				str_buffer += dt_current_day.getDate()+"</font></a></td>\n";
				dt_current_day.setDate(dt_current_day.getDate()+1);
		}
		// print row footer
		str_buffer += "</tr>\n";
	}
	// print calendar footer
	str_buffer +=
		"<form name=\"cal\">\n<tr><td colspan=\"7\" bgcolor=\"#336699\">"+
		"<font color=\"white\" face=\"tahoma, verdana\" size=\"2\">"+
		"<input type=\"hidden\" name=\"time\" value=\""+dt2tmstr(dt_datetime)+
		"\" size=\"8\" maxlength=\"8\"></font></td></tr>\n</form>\n" +
		"</table>\n" +
		"</tr>\n</td>\n</table>\n" +
		"</body>\n" +
		"</html>\n";

	var vWinCal = window.open("", "Calendar", 
		"width=200,height=220,status=no,resizable=yes,top=200,left=200");
	vWinCal.opener = self;
	var calc_doc = vWinCal.document;
	calc_doc.write (str_buffer);
	calc_doc.close();
}
// datetime parsing and formatting routimes. modify them if you wish other datetime format
function str2dt (str_datetime) {
	var re_date = /^(\d+)\/(\d+)\/(\d+)/;
	if (!re_date.exec(str_datetime))
		return alert("Invalid Datetime format: "+ str_datetime);
	return (new Date (RegExp.$3, RegExp.$2-1, RegExp.$1, RegExp.$4, RegExp.$5, RegExp.$6));
}
function dt2dtstr (dt_datetime) {
	return (new String (
			dt_datetime.getDate()+"/"+(dt_datetime.getMonth()+1)+"/"+dt_datetime.getFullYear()+""));
}
function dt2tmstr (dt_datetime) {
	//return (new String (
			//dt_datetime.getHours()+":"+dt_datetime.getMinutes()+":"+dt_datetime.getSeconds()));
			return ""
}

