parseDate用于解析字符串输入并转换为Date对象。您不应该使用parseDate。而是使用formatDate
<c:forEach items="${employees}" var="employee" varStatus="loop">
var contentString = '<div id="content">' +
'<h1 id="firstheading" class="firstheading" style="font-size: 11px;"><p style="color: green">
<fmt:formatDate type="time" value="${employee.startDate.time}" pattern="HH:mm dd/MM/yyyy z"/></p> to <p style="color: orange">
<fmt:formatDate type="time" value="${employee.endDate.time}" pattern="HH:mm dd/MM/yyyy z" /></p></h1>' +
'<div id="bodyContent">' +
'<p style="font-size: 14px;">${employee.details}</p>' +
'</div>' +
'</div>';
</c:forEach>