Nonexisting field error while accessing user birthday in Facebook Android API – Facebook api

I want to access the user birthday & gender, but I am getting an error when I try to access the birthday.I am using the Facebook SDK version facebook-android-sdk:4.18.0.

It gives me this error:

{Response: responseCode: 400, graphObject: null, error: {HttpStatus:
400, errorCode: 100, errorType: OAuthException, errorMessage: (#100)
Tried accessing nonexisting field (user_birthday) on node type
(User)}}

Here is my code:

public class MainActivity extends AppCompatActivity {
    private CallbackManager callbackManager;
    private TextView info;
    private LoginButton loginButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FacebookSdk.sdkInitialize(getApplicationContext());
        callbackManager = CallbackManager.Factory.create();

        setContentView(R.layout.activity_main);
        info = (TextView)findViewById(R.id.info);
        loginButton = (LoginButton)findViewById(R.id.login_button);
        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                GraphRequest request = GraphRequest.newMeRequest(
                        loginResult.getAccessToken(),
                        new GraphRequest.GraphJSONObjectCallback() {
                            @Override
                            public void onCompleted(JSONObject object, GraphResponse response) {
                                Log.v("LoginActivity", response.toString());

                                // Application code
                                String email = object.optString("email");
                                String birthday = object.optString("birthday");
                                String name = object.optString("name"); // 01/31/1980 format
                                info.setText("email:  " +
                                        email + "n" +
                                        "birthday " + birthday+
                                "n name"+name);
                            }
                        });
                Bundle parameters = new Bundle();
                parameters.putString("fields", "id,name,email,gender,user_birthday");
                request.setParameters(parameters);
                request.executeAsync();

            }

            @Override
            public void onCancel() {
                info.setText("Login attempt cancelled.");
            }

            @Override
            public void onError(FacebookException e) {
                info.setText("Login attempt failed.");
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }
}