"You Must Be Born Again"
As the story goes, a "ruler of the Jews" named Nicodemus came to Jesus under the cover of the night and told Jesus that "they" (who Nicodemus represented) knew he was a teacher of God - basing the knowledge on the observation that no one could do the things these Jesus did, unless God was with him.Interestingly, Jesus didn't respond by agreeing or thanking Nicodemus. Instead he went straight into telling Nicodemus that "unless one is born again he cannot "see the kingdom of God" which immediately surprised and confused Nicodemus who took the phrase literally and queried how an old man could possibly enter his mothers womb a second time and be born.
Jesus explained that he was not referring to being born again in the manner of a mother giving birth, but of another type of birth. A rebirth which involved something else entirely - yet significantly similar. Being born once gave one, a human experience. Being born again, gave that human an understanding of what The Kingdom of God was. Without that, a human being would not be able to enter into that knowledge.
Jesus then added a mystical phrase about a wilful wind which one can hear but not know where that wind comes from or where it goes, saying that this is what it is like for everyone born again (of the spirit).
Nicodemus still didn't understand and Jesus mentioned the irony of how a learned teacher of Israel could have trouble in understanding what Jesus was saying and pointed out that the witness given to Nicodemus was not received because it was not understood
My understanding of "being born again of the spirit" is that one has to completely disregard everything they ever learned - everything ever told to them as being true or false and start again, through learning from GOD directly.
The conception and gestation period happens first and the time that this takes is specific to each individual. One is not simply born again in an instant.