Much of historic literature is in fact written long after the event, in fact in many cases hundreds of years later. However the Books of the BIBLE that make up the New Testament were in fact written by eye witnesses of the Resurrection, and as far as the Gospels are concerned that speak of Christ raised from the dead, we see below that they must have been written BEFORE the fall of Jerusalem in 70AD....
The first three Gospels, and possibly also the fourth, were apparently written while the city of Jerusalem was still standing. Each of the first three Gospels contains predictions by Jesus concerning the destruction of Jerusalem and the Temple (Matthew 24; Mark 13; Luke 21), but none records the fulfillment. We know that Titus the Roman destroyed the city and Temple in A.D. 70. Hence, the composition of the first three Gospels most likely occurred sometime before this event, otherwise their destruction would have been recorded. The fact that all four gospels are written from the perspective that the city of Jerusalem and the temple had not been destroyed gives evidence of an early date.