# 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.
""" Add key and bucket parameters to starting URL query string. """
    parsed = urlparse.urlparse(starting_url)
    query = collections.OrderedDict(urlparse.parse_qsl(parsed.query))
    query.update([('key', key), ('bucket', bucket)])
    redirect_url = urlparse.urlunparse((
        parsed.scheme, parsed.netloc, parsed.path,
        parsed.params, urlparse.urlencode(query), None))
    return redirect_url
def is_bucket_specified_in_domain_name(path, headers):
    host = headers.get('host', '')
    return re.match(r'.*s3(\-website)?\.([^\.]+\.)?amazonaws.com', host)
def is_object_specific_request(path, headers):
    """ Return whether the given request is specific to a certain S3 object.
        Note: the bucket name is usually specified as a path parameter,
        but may also be part of the domain name! """
    bucket_in_domain = is_bucket_specified_in_domain_name(path, headers)
    parts = len(path.split('/'))
    return parts > (1 if bucket_in_domain else 2)
def normalize_bucket_name(bucket_name):
    bucket_name = bucket_name or ''
    
    bucket_name = bucket_name.lower()
    return bucket_name
def get_key_name(path, headers):
    parsed = urlparse.urlparse(path)
    path_parts = parsed.path.lstrip('/').split('/', 1)
    if uses_path_addressing(headers):
        return path_parts[1]
    return path_parts[0]
def uses_path_addressing(headers):