# 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.
if not query:
            return True
        
        contains_cred = 'X-Amz-Credential' in query and 'X-Amz-Signature' in query
        contains_key = 'AWSAccessKeyId' in query and 'Signature' in query
        if (method == 'POST' and query.startswith('uploadId')) or contains_cred or contains_key:
            return True
    def forward_request(self, method, path, data, headers):
        
        parsed_path = urlparse.urlparse(path)
        
        
        if 's3.amazonaws.com' not in headers.get('host', ''):
            headers['host'] = 'localhost'
        
        if 'Content-MD5' in headers and not self.is_s3_copy_request(headers, path):
            response = check_content_md5(data, headers)
            if response is not None:
                return response
        modified_data = None
        
        bucket_name = get_bucket_name(path, headers)
        if method == 'PUT' and not re.match(BUCKET_NAME_REGEX, bucket_name):
            if len(parsed_path.path) <= 1:
                return error_response('Unable to extract valid bucket name. Please ensure that your AWS SDK is ' +
                    'configured to use path style addressing, or send a valid <Bucket>.s3.amazonaws.com "Host" header',
                    'InvalidBucketName', status_code=400)
            return error_response('The specified bucket is not valid.', 'InvalidBucketName', status_code=400)