# Type of request: This is a bug report

# Detailed description
S3 list buckets returns a different format for CreationDate than the one expected by the Java SDK and parsing fails. Using Java SDK 2.13.39. Also verified w/ .40, .38, .30 and .20. Will check previous Docker releases for localstack.

``Unable to unmarshall response (Text '2020-06-17T15:26:46.032838+00:00' could not be parsed at index 19). Response Code: 200, Response Text: 
software.amazon.awssdk.core.exception.SdkClientException: Unable to unmarshall response (Text '2020-06-17T15:26:46.032838+00:00' could not be parsed at index 19). Response Code: 200, Response Text: <truncated...>
``

## Expected behavior
Return CreationDate in same format as the actual S3 API call.

## Actual behavior
Returns CreationDate in slightly different format from the actual S3 API call. Fractional seconds are included.

# Steps to reproduce
Run "aws s3api list-buckets" vs "aws s3api list-buckets --endpoint-url http://localstack:4566" and note different date format for CreationDate.

## Command used to start LocalStack
docker-compose:
```
  localstack:
    image: localstack/localstack
    ports:
      - '4566:4566'
    environment:
      SERVICES: s3
      DEBUG: 1
```
## Client code (AWS SDK code snippet, or sequence of "awslocal" commands)
See steps to reproduce.
bucket_name = normalize_bucket_name(bucket_name)
    for bucket, notifs in S3_NOTIFICATIONS.items():
        if bucket == bucket_name:
            action = {'PUT': 'ObjectCreated', 'POST': 'ObjectCreated', 'DELETE': 'ObjectRemoved'}[method]
            
            
            if action == 'ObjectCreated' and method == 'POST':
                api_method = 'CompleteMultipartUpload'
            else:
                api_method = {'PUT': 'Put', 'POST': 'Post', 'DELETE': 'Delete'}[method]
            event_name = '%s:%s' % (action, api_method)
            for notif in notifs:
                send_notification_for_subscriber(notif, bucket_name, object_path,
                    version_id, api_method, action, event_name)
def send_notification_for_subscriber(notif, bucket_name, object_path, version_id, api_method, action, event_name):
    bucket_name = normalize_bucket_name(bucket_name)
    if not event_type_matches(notif['Event'], action, api_method) or \
            not filter_rules_match(notif.get('Filter'), object_path):
        return
    key = urlparse.unquote(object_path.replace('//', '/'))[1:]
    s3_client = aws_stack.connect_to_service('s3')