# 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 isinstance(allowed_origins, list):
        return allowed_origins
    return [allowed_origins]
def append_cors_headers(bucket_name, request_method, request_headers, response):
    bucket_name = normalize_bucket_name(bucket_name)
    cors = BUCKET_CORS.get(bucket_name)
    if not cors:
        return
    origin = request_headers.get('Origin', '')
    rules = cors['CORSConfiguration']['CORSRule']
    if not isinstance(rules, list):
        rules = [rules]
    for rule in rules:
        
        allowed_methods = rule.get('AllowedMethod', [])
        if request_method in allowed_methods:
            allowed_origins = rule.get('AllowedOrigin', [])
            
            
            allowed_origins = convert_origins_into_list(allowed_origins)
            for allowed in allowed_origins:
                if origin in allowed or re.match(allowed.replace('*', '.*'), origin):
                    response.headers['Access-Control-Allow-Origin'] = origin
                    if 'ExposeHeader' in rule:
                        expose_headers = rule['ExposeHeader']
                        response.headers['Access-Control-Expose-Headers'] = \
                            ','.join(expose_headers) if isinstance(expose_headers, list) else expose_headers
                    break
def append_aws_request_troubleshooting_headers(response):