The Other Language Problem

For some of the ages we write, we might decide to have people living there. And since this is Uru, some of these people will keep journals. Of course they won't speak English, or any other surface language. How are we going to make the journals understandable? It would be useless to have them in a totally new language without translations, but if we do "translate" them, there is the question "How did you learn the language so fast? You only wrote the age a few days ago!" So what are we going to do about that?