function show_calendar(str_target, str_datetime) {
 var arr_months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
// var arr_months = ["一月", "二月", "三月", "四月", "五月", "六月", "七月", "八月", "九月", "十月", "十一月", "十二月"]
 var week_days = ["Su", "Mo", "Tu", "We", "Th", "Fr", "Sa"];
// var week_days = ["日", "一", "二", "三", "四", "五", "六"];
 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=\"#4682B4\" style=\"MARGIN: 0px\" bgcolor=\"White\">\n"+
 "<table class=\"clsOTable\" cellspacing=\"0\" border=\"0\" width=\"100%\">\n"+
 "<tr><td bgcolor=\"#4682B4\">\n"+
 "<table cellspacing=\"1\" cellpadding=\"3\" border=\"0\" width=\"100%\">\n"+
 "<tr>\n <td bgcolor=\"#4682B4\"><a href=\"javascript:window.opener.show_calendar('"+
 str_target+"', '"+ dt2dtstr(dt_prev_month)+"'+document.cal.time.value);\">"+
 "<img src=\"/images/common/prev.gif\" width=\"16\" height=\"16\" border=\"0\""+
 " alt=\"previous month\"></a></td>\n"+
 " <td bgcolor=\"#4682B4\" colspan=\"5\">"+
 "<font color=\"white\" face=\"tahoma, verdana\" size=\"2\">"
 +arr_months[dt_datetime.getMonth()]+" "+dt_datetime.getFullYear()+"</font></td>\n"+
 " <td bgcolor=\"#4682B4\" align=\"right\"><a href=\"javascript:window.opener.show_calendar('"
 +str_target+"', '"+dt2dtstr(dt_next_month)+"'+document.cal.time.value);\">"+
 "<img src=\"/images/common/next.gif\" width=\"16\" height=\"16\" 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=\"#87CEFA\">"+
 "<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=\"#FFB6C1\" align=\"right\">";
 else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6)
 // weekend days
 str_buffer += " <td bgcolor=\"#DBEAF5\" 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=\"#87CEFA\">"+
 "<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=200,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));
 return (new Date (RegExp.$1, RegExp.$2-1, RegExp.$3, '0', '0', '0'));
}

function dt2dtstr (dt_datetime) {
 var monthis=(dt_datetime.getMonth()+1);
 var dayis=dt_datetime.getDate();
 if(monthis<10) {
 monthis='0'+monthis;
 }
 if(dayis<10) {
 dayis='0'+dayis;
 }

 return (new String (
 dt_datetime.getFullYear()+"-"+monthis+"-"+dayis));
}

function dt2tmstr (dt_datetime) {
 return '';
// return (new String (
// dt_datetime.getHours()+":"+dt_datetime.getMinutes()+":"+dt_datetime.getSeconds()));
}
