-That's not the only problem with this letter. The year is indicated there, based on the birth of Christ.
-The birth of Christ?
-The dating system isn't used anymore. It's derived from an ancient religion, one that hasn't been practiced for centuries. That date was 400 years ago.
(De Fullmetal Alchemist. Hay algo de los mundos posapocalipticos de Ernst Jünger acá).