function checkdate(objName) {
var datefield = objName;
var error;

error=0;

if (objName.value!=""){
	if ((objName.value.length<10)||(objName.value.length>10)){
		alert("La fecha es incorrecta.Formato: dd/mm/aaaa");
		datefield.value="";
		datefield.focus();
		return false;
	}else{
		var dias=objName.value.charAt(0) + objName.value.charAt(1);
		var meses=objName.value.charAt(3) + objName.value.charAt(4);
		var anos=objName.value.charAt(6) + objName.value.charAt(7) + objName.value.charAt(8) + objName.value.charAt(9);
		var i;
		var patron1;
		patron1="0123456789";	
		
		if ((objName.value.charAt(2)!='/')||(objName.value.charAt(5)!='/')){
			error=1;
			alert("La fecha es incorrecta.Formato: dd/mm/aaaa");
			datefield.value="";
			datefield.focus();
			return false;	
		};
		
		if (error==0){
			for(i = 0; i <= 3; i++){
				if(patron1.search(anos.charAt(i)) < 0){
					error=1;
					alert("La fecha es incorrecta.Formato: dd/mm/aaaa");
					datefield.value="";
					datefield.focus();
					return false;	
				};				
			};
		};
		
		if (error==0){
			if (chkdate(objName) == false) {
				datefield.select();
				alert("La fecha es incorrecta.Formato: dd/mm/aaaa");
				datefield.value=""
				datefield.focus();
				return false;
			}else {
				return true;
			};
		};
	};
};
};

function chkdate(objName) {
	var strDatestyle = "EU";  //European date style
	var strDate;
	var strDateArray;
	var strDay;
	var strMonth;
	var strYear;
	var intday;
	var intMonth;
	var intYear;
	var booFound = false;
	var datefield = objName;
	var strSeparatorArray = new Array("/");
	var intElementNr;
	var err = 0;
	var strMonthArray = new Array(12);
	strMonthArray[0] = "01";
	strMonthArray[1] = "02";
	strMonthArray[2] = "03";
	strMonthArray[3] = "04";
	strMonthArray[4] = "05";
	strMonthArray[5] = "06";
	strMonthArray[6] = "07";
	strMonthArray[7] = "08";
	strMonthArray[8] = "09";
	strMonthArray[9] = "10";
	strMonthArray[10] = "11";
	strMonthArray[11] = "12";
	strDate = datefield.value;
	if (strDate.length < 1) {
		return true;
	}
	if (strDate.indexOf("/")==-1){
		return false;
	}
	
for (intElementNr = 0; intElementNr < strSeparatorArray.length; intElementNr++) {
if (strDate.indexOf(strSeparatorArray[intElementNr]) != -1) {
strDateArray = strDate.split(strSeparatorArray[intElementNr]);
if (strDateArray.length != 3) {
err = 1;
return false;
}
else {
strDay = strDateArray[0];
strMonth = strDateArray[1];
strYear = strDateArray[2];
}
booFound = true;
   }
}
if (booFound == false) {
if (strDate.length>5) {
strDay = strDate.substr(0, 2);
strMonth = strDate.substr(2, 2);
strYear = strDate.substr(4);
   }
}
if (strYear.length == 2) {
strYear = '20' + strYear;
}
// US style
if (strDatestyle == "US") {
strTemp = strDay;
strDay = strMonth;
strMonth = strTemp;
}
intday = parseInt(strDay, 10);
if (isNaN(intday)) {
err = 2;
return false;
}
intMonth = parseInt(strMonth, 10);
if (isNaN(intMonth)) {
for (i = 0;i<12;i++) {
if (strMonth.toUpperCase() == strMonthArray[i].toUpperCase()) {
intMonth = i+1;
strMonth = strMonthArray[i];
i = 12;
   }
}
if (isNaN(intMonth)) {
err = 3;
return false;
   }
}
intYear = parseInt(strYear, 10);
if (isNaN(intYear)) {
err = 4;
return false;
}
if (intMonth>12 || intMonth<1) {
err = 5;
return false;
}
if ((intMonth == 1 || intMonth == 3 || intMonth == 5 || intMonth == 7 || intMonth == 8 || intMonth == 10 || intMonth == 12) && (intday > 31 || intday < 1)) {
err = 6;
return false;
}
if ((intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) && (intday > 30 || intday < 1)) {
err = 7;
return false;
}
if (intMonth == 2) {
if (intday < 1) {
err = 8;
return false;
}
if (LeapYear(intYear) == true) {
if (intday > 29) {
err = 9;
return false;
}
}
else {
if (intday > 28) {
err = 10;
return false;
}
}
}
if (strDatestyle == "US") {
datefield.value = strMonthArray[intMonth-1] + " " + intday+" " + strYear;
}
else {
	if (intday<10){
		datefield.value = "0" + intday + "/" + strMonthArray[intMonth-1] + "/" + strYear;
	}else{
		datefield.value = intday + "/" + strMonthArray[intMonth-1] + "/" + strYear;
	}
}
return true;
}

function LeapYear(intYear) {
if (intYear % 100 == 0) {
if (intYear % 400 == 0) { return true; }
}
else {
if ((intYear % 4) == 0) { return true; }
}
return false;
}