def validate_request_timestamp(req_body, max_diff=<NUM_LIT>):
time_str = req_body.get('<STR_LIT>', {}).get('<STR_LIT>')<EOL>if not time_str:<EOL><INDENT>log.error('<STR_LIT>', req_body)<EOL>return False<EOL><DEDENT>req_ts = datetime.strptime(time_str, "<STR_LIT>")<EOL>diff = (datetime.utcnow() - req_ts).total_seconds()<EOL>if abs(diff) > max_diff:<EOL><INDENT>log.error('<STR_LIT>', diff)<EOL>return False<EOL><DEDENT>return True<EOL>
Ensure the request's timestamp doesn't fall outside of the
    app's specified tolerance.

    Returns True if this request is valid, False otherwise.

    :param req_body: JSON object parsed out of the raw POST data of a request.
    :param max_diff: Maximum allowable difference in seconds between request
        timestamp and system clock. Amazon requires <= 150 seconds for
        published skills.