How to use the angular-highcharts.Highcharts.dateFormat function in angular-highcharts

$scope.dashboardXHR = httpGet('/admin/dashboard', function(data) {
                $scope.dashboard = data;

                // 如果启用了 ga chart
                if ($scope.dashboard.ga_enable) {
                    $scope.getTopPages();
                    $scope.getDailyVisit();
                    $scope.getBrowser();
                }
                else {
                    $scope.nowDate = Highcharts.dateFormat('%m月%d日', new Date().getTime());
                }
            });
        };