Thank you for the question on the dating of the Gospel of John, “In which time was the book of John written?”
There are two dates for the writing of the Gospel of John. The dates are before 70 CE or around 85 CE.
Among the various pros and cons for the dates, the critical question is the Fall of Jerusalem in 70 CE by General Titus of the Roman Army. The destruction of Jerusalem and the Temple would have been known to the Apostle John if the Gospel of John was written after this major catastrophic event in Israel.
If it was written after 70 CE, one would think that John would make a reference to it that what Jesus declared in Matthew 24. The text says this, “Jesus left the temple and was walking away when his disciples came up to him to call his attention to its buildings. 2 “Do you see all these things?” he asked. “Truly I tell you, not one stone here will be left on another; every one will be thrown down.” 3 As Jesus was sitting on the Mount of Olives, the disciples came to him privately. “Tell us,” they said, “when will this happen, and what will be the sign of your coming and of the end of the age?” 4 Jesus answered: “Watch out that no one deceives you. 5 For many will come in my name, claiming, ‘I am the Messiah,’ and will deceive many. 6 You will hear of wars and rumors of wars, but see to it that you are not alarmed. Such things must happen, but the end is still to come. 7 Nation will rise against nation, and kingdom against kingdom. There will be famines and earthquakes in various places. 8 All these are the beginning of birth pains…” (NIV).
The lack of mentioning the destruction of the Temple would be highly questionable if the Gospel of John was written about 85 CE. This would have been an affirmation of Jesus’ words being fulfilled. In my opinion, the lack of mentioning of the destruction of the Temple would indicate that the Temple was still in existence at the time of his writing of the Gospel of John.
In the 25–30 years after the death and resurrection of Jesus Christ, witnesses of Jesus’ words and works are aging and dying. The Apostle John and his fellow apostles would be in their sixties by this time. They would have been considered old with some of them having died. The destruction would have scattered the Jews and the Christians beyond Israel.
Summary: Could the Apostle John ignored or neglect to mention the Fall of Jerusalem in the Gospel of John? It is unlikely.
-Kingston