Ανέκαθεν is an ancient Greek word which has survived in modern Greek and it means “από πάντα” (ever since, all along, always). “Ανέκαθεν” is used when we want to refer to something that started in the past and continues up to now.
Αυτός ανέκαθεν δούλευε πολλές ώρες.
He has always been working many hours.
When we refer to the future, we use “πάντα” instead:
Πάντα θα σε αγαπάω.
I will always love you.