Angular ui-grid Date format

Hi, I am trying to format the Date column in angular ui-grid(version 3.2.8) But it is not working.
The Dates are passing to getCellFormatDate function as Ex: 2016-09-27 15:18:26 But it is returning 0(zero). Plz suggest how to return it as
yyyy-MM-dd  

Grid columns definition

$scope.gridOptions = {
data: 'mydata',
enableRowSelection: true,
multiSelect: false,
enableColumnResize: true,
columnDefs: [
{ field: 'startDate', displayName: 'Date',type: 'date', 
cellTemplate: <div>{{grid.appScope.getCellFormatDate(row.entity.startDt}}</div>}]};

JavaScript code

$scope.getCellFormatDate = function(dt)
{
$scope.dtFormated = dt |'date:\'yyyy-MM-dd\'';
return $scope.dtFormatted;
};

Thanks