function show_calendar(str_target, str_datetime) {
	// ARRAYS ANZEIGE
	var arr_months = ["Januar", "Februar", "März", "April", "Mai", "Juni", "Juli", "August", "September", "Oktober", "November", "Dezember"];
	var week_days = ["So", "Mo", "Di", "Mi", "Do", "Fr", "Sa"];
	var n_weekstart = 1; // TAG AN WELCHEM DIE WOCHE STARTET (0=Sonntag, 1=Montag, usw.)

	var dt_datetime = (str_datetime == null || str_datetime =="" ?  new Date() : string2date(str_datetime));
	var dt_prev_month = new Date(dt_datetime);
	dt_prev_month.setMonth(dt_datetime.getMonth()-1);
	if (dt_datetime.getMonth()%12 != (dt_prev_month.getMonth()+1)%12) {
		dt_prev_month.setMonth(dt_datetime.getMonth());
		dt_prev_month.setDate(0);
	}
	var dt_next_month = new Date(dt_datetime);
	dt_next_month.setMonth(dt_datetime.getMonth()+1);
	if ((dt_datetime.getMonth() + 1)%12 != dt_next_month.getMonth()%12) {
		dt_next_month.setDate(0);
	}	
	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 OUTPUT TITEL
	var str_buffer = new String (
		"<html>\n"+
		"<head>\n"+
		"<title>Kalender</title>\n"+
		"<style type=\"text/css\">"+
		".monat { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #FFFFFF; line-height: 12pt }"+
		".wochentag { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #FFFFFF; line-height: 12pt }"+
		"a.tage_aktueller_monat:link { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #000000; text-decoration: underline; line-height: 12pt }"+
		"a.tage_aktueller_monat:visited { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #000000; text-decoration: underline; line-height: 12pt }"+
		"a.tage_aktueller_monat:hover { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #666666; text-decoration: underline; line-height: 12pt }"+
		"a.tage_anderer_monat:link { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #666666; text-decoration: underline; line-height: 12pt }"+
		"a.tage_anderer_monat:visited { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #666666; text-decoration: underline; line-height: 12pt }"+
		"a.tage_anderer_monat:hover { font-family: Verdana, Arial, sans-serif; font-size: 9pt; font-weight: normal; color: #999999; text-decoration: underline; line-height: 12pt }"+
		"</style>"+
		"</head>\n"+
		"<body bgcolor=\"#FFFFFF\">\n"+
		"<table cellspacing=\"0\" border=\"0\" width=\"100%\">\n"+
		"<tr><td bgcolor=\"#666666\">\n"+
		"<table cellspacing=\"1\" cellpadding=\"3\" border=\"0\" width=\"100%\">\n"+
		"<tr>\n	<td bgcolor=\"#666666\"><a href=\"javascript:window.opener.show_calendar('"+
		str_target+"', '"+ date2string(dt_prev_month)+"');\">"+
		"<img src=\"navigation/s_kalender_back01.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"vorheriger monat\"></a></td>\n"+
		"	<td bgcolor=\"#666666\" colspan=\"5\" class=\"monat\">"+
		arr_months[dt_datetime.getMonth()]+" "+dt_datetime.getFullYear()+"</td>\n"+
		"	<td bgcolor=\"#666666\" align=\"right\"><a href=\"javascript:window.opener.show_calendar('"
		+str_target+"', '"+date2string(dt_next_month)+"');\">"+
		"<img src=\"navigation/s_kalender_next01.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"nächster monat\"></a></td>\n</tr>\n"
	);

	var dt_current_day = new Date(dt_firstday);
	// HTML OUTPUT WOCHENTAGE TITEL
	str_buffer += "<tr>\n";
	for (var n=0; n<7; n++)
		str_buffer += "	<td bgcolor=\"#999999\" class=\"wochentag\" align=\"center\">"+
		week_days[(n_weekstart+n)%7]+"</td>\n";
	// HTML OUTPUT KALENDER-TABELLE
	str_buffer += "</tr>\n";
	while (dt_current_day.getMonth() == dt_datetime.getMonth() ||
		dt_current_day.getMonth() == dt_firstday.getMonth()) {
		// HTML OUTPUT KOPF
		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())
					// AKTUELLES DATUM
					str_buffer += "	<td bgcolor=\"#FF0000\" align=\"center\">";
				else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6)
					// WOCHENENDEN
					str_buffer += "	<td bgcolor=\"#EEEEEE\" align=\"center\">";
				else
					// ARBEITSTAGE
					str_buffer += "	<td bgcolor=\"#FFFFFF\" align=\"center\">";

				if (dt_current_day.getMonth() == dt_datetime.getMonth())
					// TAGE DES AKTUELLEN MONATS
					str_buffer += "<a href=\"javascript:window.opener."+str_target+
					".value='"+date2string(dt_current_day)+"'; window.close();\" class=\"tage_aktueller_monat\">";
				else 
					// TAGE EINES ANDERN MONATS
					str_buffer += "<a href=\"javascript:window.opener."+str_target+
					".value='"+date2string(dt_current_day)+"'; window.close();\" class=\"tage_anderer_monat\">";
				str_buffer += dt_current_day.getDate()+"</a></td>\n";
				dt_current_day.setDate(dt_current_day.getDate()+1);
		}
		// HTML OUTPUT FUSS
		str_buffer += "</tr>\n";
	}
	// HTML OUTPUT TABELLEN-ENDE
	str_buffer +=
		"</table>\n" +
		"</tr>\n</td>\n</table>\n" +
		"</body>\n" +
		"</html>\n";

	var vWinCal = window.open("", "kalender", "width=200,height=220,status=no,resizable=no,top=200,left=200");
	vWinCal.opener = self;
	vWinCal.focus();
	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 string2date(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));
}
function date2string(dt_datetime) {
	return (new String (
			dt_datetime.getDate()+"."+(dt_datetime.getMonth()+1)+"."+dt_datetime.getFullYear()));
}

