If one were to write a false account about historical events one would have to either do it long after the event took place or out of the region where the event took place otherwise people would be able to expose the lies. We know that it was written early because the bible is an account of historical events and we can determine when it was written because of what is not recorded. For example the destruction of the second temple in 70 AD. No where is this monumental event mentioned in the New Testament there for we know it was written before 70 AD when many eyewitnesses were still alive. Scholars have also determined dates of individual books and they are all before 70 AD. If the accounts including miracles were untruth they would have been exposed by the eyewitnesses and not propagated.