code: function _scheduleRealCallback() {
      if (_realCallbackKey) {
          global.clearTimeout(_realCallbackKey);
      }
  
      const first = _callbackList[0];
  
      if (!first) {
          debuglog("_scheduleRealCallback: no more callbacks, not rescheduling");
          return;
      }
  
      const now = _now();
      const delayMs = Math.min(first.runAt - now, TIMER_CHECK_PERIOD_MS);
  
      debuglog("_scheduleRealCallback: now:", now, "delay:", delayMs);
      _realCallbackKey = global.setTimeout(_runCallbacks, delayMs);
  }
docs: use the real global.setTimeout to schedule a callback to _runCallbacks.