jquery validade custom 18+

validator.js

$.validator.addMethod('eighteenOrOlder', function(v, el) {
    var month = $('input[name="dobMonth"]').val();
    var day = $('input[name="dobDay"]').val();
    var year = $('input[name="dobYear"]').val();
    var birthDate = new Date();
    birthDate.setFullYear(year, month - 1, day);
    var currDate = new Date();
    currDate.setFullYear(currDate.getFullYear() - 18);
    if ((currDate - birthDate) > 0) {
        return true;
    } else {
        return false;
    }
}, "You must be over 18 to be eligible to participate.");