function cierracalendar(){	
	divi= document.getElementById('calend');
	divi.style.display= 'none';	
}
function cierracalendarx(aaa,bbb){
	divi= document.getElementById('calend');
	divi.style.display= 'none';
	d1= eval(bbb);
	d1.value= aaa;
}
function show_calendar(str_target, str_datetime) {
	divi= document.getElementById('calend');
	var arr_months = ["January", "February", "March", "April", "May", "Jun", "July", "August", "September", "October", "November", "December"];
	var week_days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];
	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 (
		"<table cellspacing=\"0\" cellpadding=\"0\" border=\"0\" width=\"100%\">\n"+
			"<tr>\n"+
				"<td>\n"+
				"<table cellspacing=\"0\" cellpadding=\"0\" border=\"0\" width=\"100%\">\n"+
					"<tr>\n"+
						"<td background=\"images/cal_bg.gif\">\n"+
							"<a href=\"javascript:show_calendar('"+str_target+"', '"+ dt2dtstr(dt_prev_month)+"');\">\n"+
								"<img src=\"images/prev.gif\" width=\"30\" height=\"30\" border=\"0\" alt=\"previous month\">\n"+
							"</a>\n"+
						"</td>\n"+
						"<td height=\"30\" colspan=\"5\" align=\"center\" background=\"images/cal_bg.gif\" class=\"texto_bold_blanco\">\n"+
							""+arr_months[dt_datetime.getMonth()]+" "+dt_datetime.getFullYear()+"\n"+
						"</td>\n"+
						"<td align=\"right\" background=\"images/cal_bg.gif\">\n"+
							"<a href=\"javascript:show_calendar('"+str_target+"', '"+dt2dtstr(dt_next_month)+"');\">\n"+
								"<img src=\"images/next.gif\" width=\"30\" height=\"30\" border=\"0\" alt=\"next month\">\n"+
							"</a>\n"+
						"</td>\n"+
					"</tr>\n"+
				"</table>"+
				"<table cellspacing=\"0\" cellpadding=\"2\" border=\"0\" width=\"100%\" class=\"tabla_cal\">\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=\"tabla_cal_dias\">"+
					week_days[(n_weekstart+n)%7]+"</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=\"center\">";
						} else if (dt_current_day.getDay() == 0 || dt_current_day.getDay() == 6){
							// weekend days
							str_buffer += "<td bgcolor=\"#DBEAF5\" align=\"center\">";
						} else {
							// print working days of current month
							str_buffer += "<td bgcolor=\"white\" align=\"center\">";
						}
						if (dt_current_day.getMonth() == dt_datetime.getMonth()){
							// print days of current month
							str_buffer += "<a href=\"javascript:cierracalendarx('"+dt2dtstr(dt_current_day)+"','" +str_target+ "');\" class=\"cal_estemes\">";
						} else {
							// print days of other months
							str_buffer += "<a href=\"javascript:cierracalendarx('document.forma."+str_target+".value='"+dt2dtstr(dt_current_day)+"');\" class=\"cal_siguientemes\">";
						}
						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 += 
							"</td>\n" +
						"</tr>\n" +
					"</table>\n" +
				"</td>\n" +
			"<tr>\n" +
				"<td align=\"center\" class=\"tabla_cal_cerrar\">\n" +
					"<a href=\"javascript:cierracalendar();\" class=\"liga_blanca\">CERRAR</a>\n" +
				"</td>\n" +
			"</tr>\n" +
		"</table>\n";
//--------------------------- esto abre la ventana -----------------
	divi.style.display= 'block';
	divi.innerHTML= str_buffer;
//--------------------------- esto abre la ventana -----------------

}
// 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.$1, RegExp.$2-1, RegExp.$3, RegExp.$4, RegExp.$5, RegExp.$6));
}
function dt2dtstr (dt_datetime) {
	var aa= dt_datetime.getFullYear();
	var mm= dt_datetime.getMonth()+1;
	var dd= dt_datetime.getDate();
	if (mm<10){
		mm= "0" + mm;
	}
	if (dd<10){
		dd= "0" + dd;
	}
	var estafecha=  aa+"-"+mm+"-"+dd;
	return estafecha;			
}