function GetCookie (name) {
    var arg = name + "=";
    var alen = arg.length;
    var clen = document.cookie.length;
    var i = 0;
    while (i < clen) {
        var j = i + alen;
        if (document.cookie.substring(i, j) == arg)
        return getCookieVal (j);
        i = document.cookie.indexOf(" ", i) + 1;
        if (i == 0) break;
    }
    return null;
}
function SetCookie (name, value) {
    var argv = SetCookie.arguments;
    var argc = SetCookie.arguments.length;
    var expires = (argc > 2) ? argv[2] : null;
    var path = (argc > 3) ? argv[3] : null;
    var domain = (argc > 4) ? argv[4] : null;
    var secure = (argc > 5) ? argv[5] : false;
    document.cookie = name + "=" + escape (value) +
    ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) +
    ((path == null) ? "" : ("; path=" + path)) +
    ((domain == null) ? "" : ("; domain=" + domain)) +
    ((secure == true) ? "; secure" : "");
}
function DeleteCookie (name) {
    var exp = new Date();
    exp.setTime (exp.getTime() - 1);
    var cval = GetCookie (name);
    document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString();
}
var expDays = 1;
var exp = new Date();
exp.setTime(exp.getTime() + (expDays*24*60*60*1000));
<!------------------------------------->
function getCookieVal(offset) {
    var endstr = document.cookie.indexOf (";", offset);
    if (endstr == -1)
        endstr = document.cookie.length;
    return unescape(document.cookie.substring(offset, endstr));
}
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 = 0; // 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=\"#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=\"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=\"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='"+dt2dtstr2(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='"+dt2dtstr2(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=250,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+)\s+(\d+)\:(\d+)\:(\d+)$/;
   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 dt2dtstr2 (dt_datetime) {
   return (new String (
         (dt_datetime.getMonth()+1)+"/"+dt_datetime.getDate()+"/"+dt_datetime.getFullYear()+" "));
}

function dt2tmstr (dt_datetime) {
   //return (new String (
   return (new String (''));
         //dt_datetime.getHours()+":"+dt_datetime.getMinutes()+":"+dt_datetime.getSeconds()));
}
function dt2tmstrTMP (dt_datetime) {
   return (new String (
         dt_datetime.getHours()+":"+dt_datetime.getMinutes()+":"+dt_datetime.getSeconds()));
}

