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Under utils/common.py, 

TIMESTAMP_FORMAT_MILLIS = '%Y-%m-%dT%H:%M:%S.%fZ'

The %f produces time with microseconds, for example: 2020-03-18T19:43:18.115783Z.


However, when interacting the AWS s3 and sns apis, I receive DateTimes like this:

2020-03-02T22:32:13.240Z
i.e. milliseconds. 

This seems like a simple change to the utils. TIMESTAMP_FORMAT_MILLIS is named as if it should be millis as well. This is seems like a simple change. Is there a reason it should be microseconds?
""" Fix account ID in request payload. All external-facing responses contain our
            predefined account ID (defaults to 000000000000), whereas the backend endpoint
            from moto expects a different hardcoded account ID (123456789012). """
        return aws_stack.fix_account_id_in_arns(
            data, colon_delimiter='%3A', existing=TEST_AWS_ACCOUNT_ID, replace=MOTO_ACCOUNT_ID)
    def return_response(self, method, path, data, headers, response):
        if method == 'POST' and path == '/':
            
            data = aws_stack.fix_account_id_in_arns(data, colon_delimiter='%3A')
            aws_stack.fix_account_id_in_arns(response)
            
            search = r'<entry><key>[^<]+</key>\s*<value>\s*None\s*</[^>]+>\s*</entry>'
            response_regex_replace(response, search, '')
            
            req_data = urlparse.parse_qs(to_str(data))
            req_action = req_data['Action'][0]
            if req_action == 'Subscribe' and response.status_code < 400:
                response_data = xmltodict.parse(response.content)
                topic_arn = (req_data.get('TargetArn') or req_data.get('TopicArn'))[0]
                filter_policy = (req_data.get('FilterPolicy') or [None])[0]
                attributes = get_subscribe_attributes(req_data)
                sub_arn = response_data['SubscribeResponse']['SubscribeResult']['SubscriptionArn']
                do_subscribe(
                    topic_arn,
                    req_data['Endpoint'][0],
                    req_data['Protocol'][0],
                    sub_arn,
                    attributes,
                    filter_policy
                )