Parse date in js

<script type="text/javascript">
    var str1 = "3/01/2013";
    var str2 = "03/2/2013";

    var d1 = parseDate(str1).getTime();
    var d2 = parseDate(str2).getTime();

    if (d1 == d2) {
        alert("d1 == d2");
    }
    else if (d1 > d2) {
        alert("d1 > d2");
    }
    else {
        alert("d1 < d2");
    }

    function isDate(dateString) {

        var date = parseDate(dateString);

        if (date == null) return false;
        return true;
    }

    function parseDate(dateString) {

        var delimiter = "/";

        if (dateString.indexOf("-") > 0) {
            delimiter = "-";
        }

        var parts = dateString.split(delimiter);

        if (parts.length != 3) {
            return null;
        }

        /* mm/dd/yyyy or mm-dd-yyyy */
        var year = parts[2];
        var month = parts[0] - 1;
        var day = parts[1];

        var newDate = new Date(year, month, day);

        if (isNaN(newDate)) return null;

        if (newDate.getYear() == year
            && newDate.getMonth() == month
            && newDate.getDate() == day) {
            return newDate;
        }

        return null;
    }
</script>