AngularJS: Date filter problem

The date filter doesn't work on date strings that can be converted to Date objects via new Date()

HTML

<script src="http://code.angularjs.org/1.0.0rc1/angular-1.0.0rc1.js"></script>
<div ng:controller="Ctrl">
    <h2>Date filter fails</h2>
    <hr>
    <ul>
        <li ng:repeat="entry in entries">
            {{entry.commit.author.date | date}}
        </li>
    </ul>
    <hr>
    <h2>Date filter works</h2>
    <hr>
    <ul>
        <li ng:repeat="entry in entries">
            {{entry.getDate() | date : dd-MM-yyyy}}
        </li>
    </ul>
</div>

JavaScript

function Ctrl($scope, Commit) {
    $scope.entries = Commit.query();
}

var feed = angular.module('feed', [])
.factory('Commit', function($resource) {
    var Commit = $resource('https://api.github.com/repos/msgilligan/angular.js/commits/:sha');
                        
    Commit.prototype.getDate = function() {
        return new Date(this.commit.author.date);
    }
                        
    return Commit;
});