The Society changed the baptism vows in 1985. This is from the June 1, 1985 Watchtower:
At the close of the convention baptism talk, the baptism candidates will be in position to answer with depth of understanding and heartfelt appreciation two simple questions that serve to confirm that they recognize the implications of following Christ’s example. The first question is:
On the basis of the sacrifice of Jesus Christ, have you repented of your sins and dedicated yourself to Jehovah to do his will?
The second is:
Do you understand that your dedication and baptism identify you as one of Jehovah’s Witnesses in association with God’s spirit-directed organization?
Having answered yes to these questions, candidates are in a right heart condition to undergo Christian baptism.
These were the baptism questions from 1973 to 1985:
*** w73 5/1 280 Baptizing Follows Discipling *** If you feel the same about serving Jehovah God and taking Christ’s yoke upon you, we suggest that you consider the following two questions, which are asked of candidates for baptism:
(1) Have you repented of your sins and turned around, recognizing yourself before Jehovah God as a condemned sinner who needs salvation, and have you acknowledged to him that this salvation proceeds from him, the Father, through his Son Jesus Christ?
(2) On the basis of this faith in God and in his provision for salvation, have you dedicated yourself unreservedly to God to do his will henceforth as he reveals it to you through Jesus Christ and through the Bible under the enlightening power of the holy spirit?
Before 1973 I don't know.
