Conversation so far:
Did Geronimo attend any church?
Geronimo was raised with the traditional religious views of the Bedonkohe.
What is Geronimo's religion?
In his later years Geronimo embraced Christianity.
What is Geronimo's belief?
To the end of his life, he seemed to harbor ambivalent religious feelings.
did Geronimo attend or join any church?
Geronimo joined the Dutch Reformed Church in 1903.
Did Geronimo preach christ to people?
Geronimo advised all of my people who are not Christians, to study that religion, because it seems to me the best religion in enabling one to live right.

Question: when did he become christian
Self-contained rewrite: When did Geronimo become Christian?