// ******************************************************************
// This function accepts a string variable and verifies if it is a
// proper date or not. It validates format matching either
// mm-dd-yyyy or mm/dd/yyyy. Then it checks to make sure the month
// has the proper number of days, based on which month it is.

// The function returns true if a valid date, false if not.
// ******************************************************************

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[3]; // p@rse date into variables
day = matchArray[1];
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
}