Did it like this. Seems to be working. Though I don't like repetetive declaration of formTimeValues and calling setValue from inside setSavedTime seems odd too.

 useEffect(() => {
    const formTimeValues = getValues()?.defaultDeliveryWindow;
    if (wholeDay) {
      setSavedTime(formTimeValues);
      setValue("defaultDeliveryWindow", wholeDayRange.defaultDeliveryWindow);
    } else {
      setSavedTime((prev) => {
        setValue("defaultDeliveryWindow", prev);
      });
    }
  }, [setValue, wholeDay, getValues]);