How to get last modified date for folders in Dropbox V2 API ?

Hi,
I am trying migrate from v1 to v2 and get to the user's root folder and view all the list of files and folders with last modified date. I am passing "https://api.dropbox.com/2/files/list_folder" to get the list.

Currently I am getting "NaN/NaN/NaN" as last modified date for folders, the list is not in sorted order and size of file is not proper. And, I am also not able to open the folders.

I am using OAuthClientRequest and passing the json as 

String requestJson = "{\"path\": \"\",\"recursive\": true,\"include_media_info\": true,\"include_deleted\": false,\"include_has_explicit_shared_members\": false}";

requestQ.setBody(String.valueOf(requestJson));
requestQ.addHeader("Content-Type", "application/json");

For response I am using :

OAuthClient clientResponse = new OAuthClient(new URLConnectionClient());
OAuthResourceResponse resourceResponse= clientResponse.resource(requestQ, OAuth.HttpMethod.POST, OAuthResourceResponse.class);

Please suggest me !