JSTL timezone (KST) implementation error found

While I practicing JSTL timeZone tag, I tried to run these two actions:

<c:set var="now" value="<%= new java.util.Date() %>" />
<fmt:timeZone value="GMT+9:00">
    <fmt:formatDate value="${now}" type="both"
                    dateStyle="full" timeStyle="full"/>
</fmt:timeZone>
<%-- and --%>
<fmt:timeZone value="KST">
    <fmt:formatDate value="${now}" type="both"
                    dateStyle="full" timeStyle="full"/>
</fmt:timeZone>

I believe they should produce same result. However, they produce following two different time values.

2017년 8월 15일 화요일 오후(PM) 8시 03분 27초 GMT+09:00

2017년 8월 15일 화요일 오전(AM) 11시 03분 27초 GMT

Did I miss something or the implementation is incorrect? I case of mis-implementation, who should I contact?