When He was born of Mary being the only begotten of the Father in the flesh. However He has always been God. I already told you that.
That disagrees with what was taught in 1976:
The gospel of Jesus Christ teaches that man is an eternal being, made in the image and likeness of God. It also holds that man is a literal child of God and has the potential to, if faithful to divine laws and ordinances, of becoming like his heavenly parent. These truths are generally well understood by Latter-day Saints.
Less well understood, however, is the fact that God is an exalted man who once lived on an earth and underwent experiences of mortality. The Prophet Joseph Smith refers to this as “the great secret.” (Times and Seasons 5:613[15 Aug. 1844]. See also Joseph Smith, Teachings of the Prophet Joseph Smith, p. 345.) The progression of our Father in heaven to godhood, or exaltation, was strictly in accordance with eternal principles, for he who is not able to abide the law of a celestial kingdom cannot abide a celestial glory.” (D&C 88:22.)
By definition, exaltation includes the ability to procreate the family unit throughout eternity. This our Father in heaven has power to do. His marriage partner is our mother in heaven. We are their spirit children, born to them in the bonds of celestial marriage.
The Lord would have all his children attain exaltation, but men must have their agency. Only those who subscribe by ordinance and by faithful adherence to covenant are worthy of “a continuation of seeds forever and ever.” (D&C 132:19.)
GOD WAS ONCE A MORTAL MAN
(1-2) He Lived on an Earth like Our Own
“God himself was once as we are now, and is an exalted man and sits enthroned in yonder heavens! That is the great secret. If the veil were rent today, and the great God who holds this world in its orbit and who upholds all worlds and all things by his power was to make himself visible,–I say, if you were to see him today, you would see him like a man in form–like yourselves in all the person, image, and very form as a man; for Adam was created in the very fashion, image and likeness of God and received instruction from, and walked, talked and conversed with him, as one man talks and communes with another.” (Smith, Teachings, p. 345.)
(1-3) He Experienced Conditions Similar to Our Own and Advanced Step by Step
“Remember that God, our heavenly Father, was perhaps once a child, and mortal like we ourselves, and rose step by step in the scale of progress, in the school of advancement; has moved forward and overcome, until He has arrived at the point where He now is. “Is this really possible?” Why, my dear friends, how would you like to be governed by a ruler who has not been through all the vicissitudes of life that are common to us mortals? If he had not suffered, how could he sympathize with the distress of others? If he himself had not endured the same, how could he sympathize and be touched with the feelings of our infirmities? He could not, unless he himself had passed through the same ordeal, overcome, and overcome step by step.” (Orson Hyde in JD, 1:123.)
GOD IS NOW AN EXALTED MAN WITH POWERS OF ETERNAL INCREASE
(1-4) Our Father in Heaven Lives in an Exalted Marriage Relationship
“No matter to what heights God has attained or may attain, he does not stand alone; for side by side with him, in all her glory, a glory like unto his, stands a companion, the Mother of his children. For as we have a Father in heaven, so also we have a Mother there, a glorified, exalted, ennobled Mother.” (Melvin J. Ballard, as quoted in Bryant S. Hinckley, Sermons and Missionary Services of Melvin J. Ballard, pp. 205-6.)
... (1-20) SUMMARY
As shown in this chapter, our Father in heaven was once a man as we are now, capable of physical death. By obedience to eternal gospel principles, he progressed from one stage of life to another until he attained the state that we call exaltation or godhood. In such a condition, he and our mother in heaven were empowered to give birth to spirit children whose potential was equal to that of their heavenly parents. We are those spirit children.
Achieving a Celestial Marriage Student Manual, copyright 1976, 1992, by Corporation of the President of The Church of Jesus Christ of Latter-day Saints, p. 129 and 132
Why were we being taught that in 1976 if it is no longer true?