function show_calendar(str_target, str_datetime) {
	var arr_months = ["Styczeń", "Luty", "Marzec", "Kwiecień", "Maj", "Czerwiec",
		"Lipiec", "Sierpień", "Wrzesień", "Październik", "Listopad", "Grudzień"];
	var week_days = ["Nd", "Po", "Wt", "Śr", "Cz", "Pt", "So"];
	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"+
		"<meta http-equiv=\"Pragma\" content=\"no-cache\">\n"+
		"	<title>Calendar</title>\n"+
		"<style type=\"text/css\">"+
		"<!--"+
  
		"html"+
		"	{"+
		"	height: 100%;"+
		"	}"+
		"body"+
		"	{"+
		"	margin: 0px;"+
		"	padding: 0px;"+
		"	height: 100%;"+
		"	}"+
		"table"+
		"	{"+
		"	border: none;"+
		"	text-align: justify;"+
		"	margin-left:auto;"+
		"	margin-right:auto;"+
		"	}"+
		".tabela"+
		"	{"+
		"	height: 100%;"+
		"	width: 100%;"+
		"	}"+
		".h1"+
		"	{"+
		"	font-size: 8pt;"+
		"	text-align: center;"+
		"	font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;"+
		"	color: #666600;"+
		"	}"+
		"img"+
		"	{"+
		"	border:0;"+
		"	}"+
		"a:link"+
		"	{"+
		"	border: none;"+
		"	text-decoration: none;"+
		"	color: #666600;"+
		"	}"+
		"a:visited"+
		"	{"+
		"	text-decoration: none;"+
		"	color: #555500;"+
		"	}"+
		"a:hover"+
		"	{"+
		"	text-decoration: none;"+
		"	color: #BBBB00;"+
		"	}"+
		"a:active"+
		"	{"+
		"	text-decoration: none;"+
		"	color: #666600;"+
		"	}"+
	
		"-->"+
		"</style>"+
		"</head>\n"+
		"<body bgcolor=\"White\" style=\" margin-left: auto; margin-right auto; padding: 0px;\">\n"+
		"<table class=\"tabela\" cellspacing=\"0\">\n"+
		"<tr><td style=\"text-align: center; vertical-align: middle;\">\n"+
		"<table cellspacing=\"1\" cellpadding=\"3\" style=\"width: 180px; background-color: #666600;\">\n"+
		"<tr>\n	<td bgcolor=\"#666600\"><a href=\"javascript:window.opener.show_calendar('"+
		str_target+"', '"+ dt2dtstr(dt_prev_month)+"');\">"+
		"<img src=\"/design/prev.gif\" name=\"prev\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"Poprzedni miesiąc\" onmouseover=\"document.prev.src='/design/prev_over.gif';\" onmouseout=\"document.prev.src='/design/prev.gif';\"></a></td>\n"+
		"	<td bgcolor=\"#666600\" colspan=\"5\">"+
		"<font color=\"white\" face=\"tahoma, verdana\" size=\"2\">"
		+arr_months[dt_datetime.getMonth()]+" "+dt_datetime.getFullYear()+"</font></td>\n"+
		"	<td bgcolor=\"#666600\" align=\"right\"><a href=\"javascript:window.opener.show_calendar('"
		+str_target+"', '"+dt2dtstr(dt_next_month)+"');\">"+
		"<img src=\"/design/next.gif\" name=\"next\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"następny miesiąc\" onmouseover=\"document.next.src='/design/next_over.gif';\" onmouseout=\"document.next.src='/design/next.gif';\"></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=\"#969600\">"+
		"<font color=\"white\" 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=\"#E6E6E6\" align=\"right\">";
					
				else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6)
					// weekend days
					str_buffer += "	<td bgcolor=\"#FFFFCC\" 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)+"'; 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)+"'; 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=\"#969600\">"+
		"<font color=\"White\" face=\"tahoma, verdana\" size=\"2\">"+
		"Time: </font></td></tr>\n</form>\n" +
		"</table>\n" +
		"</tr>\n</td>\n</table>\n" +
		"</body>\n" +
		"</html>\n";

	var vWinCal = window.open("", "Calendar", 
		"width=250,height=250,status=no,resizable=no,top=200,left=200");
		 vWinCal.focus();
	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("Nieprawidłowy format daty: "+ str_datetime);
	return (new Date (RegExp.$3, RegExp.$2-1, RegExp.$1));
}
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()*/));
//}

