static ISleeper defaultSleeper() {
  ret new ISleeper {
    //Set<java.util.Timer> timers = weakSet();
    
    public Sleeping doLater(Timestamp targetSysTime, Runnable r) {
      var timer = main doLater(max(0, targetSysTime.unixDate()-sysNow()), r);
      ret new Sleeping(targetTime, r) {
        close {
          timer->cancel();
          timer = null;
        }
      };
    }
    
    public void close() {
      //cancelTimer(timer);
    }
  };
}