code: def validate_request_timestamp(req_body, max_diff=150):
      
  
      time_str = req_body.get('request', {}).get('timestamp')
  
      if not time_str:
          log.error('timestamp not present %s', req_body)
          return False
  
      req_ts = datetime.strptime(time_str, "%Y-%m-%dT%H:%M:%SZ")
      diff = (datetime.utcnow() - req_ts).total_seconds()
  
      if abs(diff) > max_diff:
          log.error('timestamp difference too high: %d sec', diff)
          return False
  
      return True
docs: 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.