Originally reported in https://github.com/localstack/localstack/issues/2099, the CreationTime for CF stacks was hardcoded. This was fixed in in LocalStack itself (https://github.com/localstack/localstack/pull/2103), but is now also fixed in moto (https://github.com/spulec/moto/pull/2818).

I don't know what version of moto you're using, and whether it's acceptable to use dev-releases, but if you do: 

moto 1.3.15.dev550 should fix this issue, so the LS fix can be removed if you upgrade :) 
def load(self):
            return policy_map
    if parsed.get('Transform') == 'AWS::Serverless-2016-10-31':
        
        region_before = os.environ.get('AWS_DEFAULT_REGION')
        if boto3.session.Session().region_name is None:
            os.environ['AWS_DEFAULT_REGION'] = aws_stack.get_region()
        try:
            transformed = transform_sam(parsed, {}, MockPolicyLoader())
            return transformed
        finally:
            os.environ.pop('AWS_DEFAULT_REGION', None)
            if region_before is not None:
                os.environ['AWS_DEFAULT_REGION'] = region_before
def get_template_body(req_data):
    body = req_data.get('TemplateBody')
    if body:
        return body
    url = req_data.get('TemplateURL')
    if url:
        response = run_safe(lambda: safe_requests.get(url, verify=False))
        
        status_code = 0 if response is None else response.status_code
        if response is None or status_code == 301 or status_code >= 400:
            
            url = convert_s3_to_local_url(url)