Issue with date picker

Here is my code
    $(function() {
        $('#dob').datepicker({
            changeMonth: true,
            changeYear: true,
            yearRange: '-65:-18'
        });
    });
Now, when I go to select a year from the drop down, say 1971, the year
changes to 1906 which is 65 years past like my first part of my date
range. Why is it doing this?
Derek