Common sense makes it very clear that, not only the Gospels, but all of the books of the New Testament were written before 70AD only about 40 years after Jesus' death and resurrection. Why? Simple. Because Jesus foretold/prophecized the destruction of both the Temple and Jerusalem.
“He wept”
Luke 19
Jesus looked over the city of Jerusalem from the height of the Mount of Olives. As He looked, He wept for the city.
“If only you had known today what would bring peace! But it is hidden from you. The days will come that your enemies will surround you without a way to escape. They will destroy this city, and there will not be one stone left on top of another.”
In fact this prophecy did come true when the Romans destroyed Jerusalem, the Temple, and most of the population was slaughetered or enslaved. THIS HAPPENED IN 70AD. Not only was the city/temple/population decimated but it marked an end to almost all of the prior Jewish rituals, such as animal sacrifices and other forms of worship.
JESUS' PROPHESY HAD COME TRUE!!!!!!!!!!!!!!
SO, THE BIG COMMON SENSE QUESTION????????? The destruction of 70AD was so monumental to all Jews and Jewish history. If any of the books of the New Testament were written after 70AD, the writers would have noted this event in their writings and pointed out that Jesus had been correct in His prophesy. But they didn't write about it because it hadn't happened prior to the time of the authoring of the New Testament.