You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Martin_Luther

Context:
In 1521 Luther dealt largely with prophecy, in which he broadened the foundations of the Reformation placing them on prophetic faith. His main interest was centered on the prophecy of the Little Horn in Daniel 8:9–12, 23–25. The antichrist of 2 Thessalonians 2 was identified as the power of the Papacy. So too was the Little Horn of Daniel 7, coming up among the divisions of Rome, explicitly applied.

Question:
When did Luther start preaching Prophetic faith?

1521