The Church of God claims that Ahn was baptized in 1948 at the age of 30 at the Naksum Sabbath Church in Incheon. However, according to the Sabbath Church's church registry, Ahn was baptized on October 9, 1954 at Haeundae Church by Pastor Kim Seok-young. Ahnsahnghong founded the Church of God in 1964 after leaving the Sabbatarian Church in 1962, and his doctrines largely mimicked or quoted those of Sabbatarian founder Ellen G. White. Ahnsahnghong's book, "Letter to the Church of Laodicea," was also directed at the Sabbatarian Church and led to his 2012 apocalypticism because he saw the Sabbatarian Church, founded in 1844, as a prophetic fulfillment of the Day of Atonement.

Ahnsahnghong's doctrine is divided into pre-1978 doctrine and post-1978 doctrine. Prior to 1978, Ahn did not deify himself as the Second Coming, but his doctrine changed when an evangelist named Uhm Soo-in published a booklet called God in the Flesh, which deified Ahn as the Second Coming who came through the prophecies of Melchizedek and David. Ahn's son, Kwang-seop Ahn, posted Ahn's booklet on his New Covenant Church of God website under the title "Personal Notes Volume 7." Volume 7, Chapter 29 is subtitled "Building the Heavenly Temple," and Ahn claims that 1971 was the end of the world. According to Ahn's interpretation, the end of the world was supposed to occur in 1844, 167 years after the founding of the Sabbath Church in 2011, but because he subtracted 40 years from 2011, he claimed that 1971 was the end.

 What is peculiar, however, is that in the tracts and handwritten notes written before 1971, there is not a single line about his baptism at age 30 or his promise to preach the gospel for 37 years, and it is not mentioned again until 1978, when Evangelist Uhm Soo-in introduced it in his tract, God in the Flesh. Ahn's sermon notes show that after 1980, he claimed on several occasions that he would start preaching the gospel at age 33 and preach for 37 years, as Evangelist Umsuin claimed. He argued that since the first coming Jesus preached for three years starting at age 30, the second coming Jesus would preach for 37 years starting at age 33. In Ahn's sermon notes from 1984, he writes that he was baptized in 1948 but was unable to learn the Bible because of the war, and that he began to learn the truth in 1951 at the age of 33. He then writes that 1988, the end of the 37 years, was his age of 70. He implied that just as David lived to be 70 years old, he would finish the whole gospel at 70 years old.

Therefore, Ahn's 1948 baptismal doctrine is believed to have been fabricated after 1980, when the Davidic doctrine was created.