function isDate(dateStr) {

var datePat = /^(\d{1,2})(\/|-)(\d{1,2})(\/|-)(\d{4})$/;
var matchArray = dateStr.match(datePat); // is the format ok?

if (matchArray == null) {
alert("Please enter date as either mm/dd/yyyy or mm-dd-yyyy.");
return false;
}

month = matchArray[1]; // p@rse date into variables
day = matchArray[3];
year = matchArray[5];

if (month < 1 || month > 12) { // check month range
alert("Month must be between 1 and 12.");
return false;
}

if (day < 1 || day > 31) {
alert("Day must be between 1 and 31.");
return false;
}

if ((month==4 || month==6 || month==9 || month==11) && day==31) {
alert("Month "+month+" doesn`t have 31 days!")
return false;
}

if (month == 2) { // check for february 29th
var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
if (day > 29 || (day==29 && !isleap)) {
alert("February " + year + " doesn`t have " + day + " days!");
return false;
}
}
return true; // date is valid
}

var win = null;
function aprifinestra(mypage,w,h){
	LeftPosition = (screen.width) ? (screen.width-w)/2 : 0;
	TopPosition = (screen.height) ? (screen.height-h)/2 : 0;
	h = h + 10;
	w = w + 10;
	settings =
	'height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars='+'no'+',resizable'
	winName = 'winName'+w+h;
	window.open(mypage,winName,settings);
}