# 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)
    exists, code, body = is_bucket_available(bucket_name)
    if not exists:
        return requests_response(body, status_code=code)
    if isinstance(to_str(encryption), six.string_types):
        encryption = xmltodict.parse(encryption)
    BUCKET_ENCRYPTIONS[bucket_name] = encryption
    return 200
def set_object_lock(bucket_name, lock_config):
    bucket_name = normalize_bucket_name(bucket_name)
    exists, code, body = is_bucket_available(bucket_name)
    if not exists:
        return requests_response(body, status_code=code)
    if isinstance(to_str(lock_config), six.string_types):
        lock_config = xmltodict.parse(lock_config)
    OBJECT_LOCK_CONFIGS[bucket_name] = lock_config
    return 200
def strip_chunk_signatures(data):
    
    
    #
    
    
    
    data_new = ''
    if data is not None:
        data_new = re.sub(b'(^|\r\n)[0-9a-fA-F]+;chunk-signature=[0-9a-f]{64}(\r\n)(\r\n$)?', b'',
            to_bytes(data), flags=re.MULTILINE | re.DOTALL)
    return data_new
def is_bucket_available(bucket_name):