From moments before His conception and during his time inside His mother's womb.
There were some who knew then that Jesus is the very Son of God... Mary, Joseph, Elizabeth and even her unborn baby inside her womb ( John the Baptizer ) all knew that the baby Mary was carrying was the very Son of God... Right after the birth of Jesus there were two, a man and a woman, who too knew and acknowledged that the bay Jesus was the very Son of God...