// Title: Timestamp picker

function show_calendar(str_target, str_date, left, top) {
	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_date = (str_date == null || str_date =="" ?  new Date() : str2dt(str_date));
	
	var dt_prev_month = new Date(dt_date);
	var dt_prev_year = new Date(dt_date);
	dt_prev_month.setMonth(dt_date.getMonth()-1);
	dt_prev_year.setYear(dt_date.getFullYear()-1);
	
	var dt_next_month = new Date(dt_date);
	var dt_next_year = new Date(dt_date);
	dt_next_month.setMonth(dt_date.getMonth()+1);
	dt_next_year.setYear(dt_date.getFullYear()+1);
	
	var dt_firstday = new Date(dt_date);
	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"+
		"	<link rel=\"stylesheet\" type=\"text/css\" href=\"include/Calendar.css\"/>\n"+
		"</head>\n"+
		"<body leftmargin=\"0\" topmargin=\"0\">\n"+
		"<table cellspacing=\"0\" border=\"0\" width=\"100%\">\n"+
		"<tr><td class=\"Calendar\">\n"+
		"<table cellspacing=\"1\" cellpadding=\"3\" border=\"0\" width=\"100%\">\n"+
		"<tr>\n	<td class=\"Calendar\"><a href=\"javascript:window.opener.show_calendar('"+
		str_target+"', '"+ dt2dtstr(dt_prev_year)+"');\">"+
		"<img src=\"images/CalPrev.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"previous year\"></a></td>\n"+
		"<td class=\"Calendar\"><a href=\"javascript:window.opener.show_calendar('"+
		str_target+"', '"+ dt2dtstr(dt_prev_month)+"');\">"+
		"<img src=\"images/CalPrev.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"previous month\"></a></td>\n"+
		"	<td class=\"MonthYear\" colspan=\"3\">"+
		arr_months[dt_date.getMonth()]+" "+dt_date.getFullYear()+"</td>\n"+
		"	<td class=\"Calendar\"><a href=\"javascript:window.opener.show_calendar('"
		+str_target+"', '"+dt2dtstr(dt_next_month)+"');\">"+
		"<img src=\"images/CalNext.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"next month\"></a></td>\n"+
		"	<td class=\"Calendar\"><a href=\"javascript:window.opener.show_calendar('"
		+str_target+"', '"+dt2dtstr(dt_next_year)+"');\">"+
		"<img src=\"images/CalNext.gif\" width=\"16\" height=\"16\" border=\"0\""+
		" alt=\"next year\"></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 class=\"Weekday\">"+
		week_days[(n_weekstart+n)%7]+"</td>\n";
	// print calendar table
	str_buffer += "</tr>\n";
	while (dt_current_day.getMonth() == dt_date.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_date.getDate() &&
					dt_current_day.getMonth() == dt_date.getMonth())
					// print current date
					str_buffer += "	<td class=\"Today\">";
				else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6)
					// weekend days
					str_buffer += "	<td class=\"Weekend\">";
				else
					// print working days of current month
					str_buffer += "	<td>";

				if (dt_current_day.getMonth() == dt_date.getMonth())
					// print days of current month
					str_buffer += "<a href=\"javascript:window.opener."+str_target+
					".value='"+dt2dtstr(dt_current_day)+"'; window.close();\">";
				else 
					// print days of other months
					str_buffer += "<a class=\"OtherMonths\" href=\"javascript:window.opener."+str_target+
					".value='"+dt2dtstr(dt_current_day)+"'; window.close();\">";
				str_buffer += dt_current_day.getDate()+"</a></td>\n";
				dt_current_day.setDate(dt_current_day.getDate()+1);
		}
		// print row footer
		str_buffer += "</tr>\n";
	}
	// print calendar footer
	str_buffer +=
		"</table>\n" +
		"</tr>\n</td>\n</table>\n" +
		"</body>\n" +
		"</html>\n";

	var vWinCal = window.open("", "Calendar", "width=180,height=205,status=no,resizable=no,top="+top+",left="+left);
	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_date) {
	var re_date = /^(\d+)\/(\d+)\/(\d+)/;
	if (!re_date.exec(str_date))
		return alert("Invalid Datetime format: "+ str_date);
	return (new Date (RegExp.$3, RegExp.$1-1, RegExp.$2));
}

function dt2dtstr (dt_date) {
	//return (new String (dt_date.getDate()+"/"+(dt_date.getMonth()+1)+"/"+dt_date.getFullYear()));
	return (new String ((dt_date.getMonth()+1)+"/"+dt_date.getDate()+"/"+dt_date.getFullYear()));
}
