[Vuejs]-Why does getter not return the value

The problem is that you are modifying the state directly with your getter, which is something you should never do. The following line modifies item.time, which you previously used to sort the items. item is a reference to the object that is stored in the state.

item.time = new Date(item.time * UNIX_TIMESTAMP).toLocaleDateString('ru-RU', DATE_OPTIONS)

To solve the issue, you can do one of two things:

• Use a different name for your rendered time

  item.renderedTime = new Date(item.time * UNIX_TIMESTAMP).toLocaleDateString('ru-RU', DATE_OPTIONS)
  

• (Shallow) copy the item so you are modifying a local copy, rather than the one in the state

  function dateToString(item) {
    const localItem = { ...item };
    localItem.time = new Date(item.time * UNIX_TIMESTAMP).toLocaleDateString(
      "ru-RU"
    );
    return localItem;
  }