"Advice is counsel about what you must do. News is a report about what has already been done. Advice urges you to make something happen. News urges you to recognize something that has already happened and to respond to it. Advice says it is all up to you to act. News says someone else has acted….The biblical Christmas texts are accounts of what actually happened in history. They are not Aesop's Fables, inspiring examples of how to live well….These Gospel narratives are telling you not what you should do but what God has done….If we are saved through our efforts, then stories about Jesus have just one function: to inspire us to imitate him and follow his example. It doesn't matter if the stories are fiction or not. What's important is that they give us examples to live by. But if we are saved by grace, not by what we do but by what he has done, then it is crucial that the great events of the Gospels - the incarnation, the atonement on the cross, and the resurrection from the dead - actually occurred in time and space….Robert Yarbrough, a New Testament scholar, says that the verbs [in 1 John 1:1] correspond to the varieties of witness attestation in ancient jurisprudence. And so when John writes, 'We have seen it and testify to it' - and then speaks of hearing, seeing, and touching - 'he is not making conversation but virtually swearing a deposition.' This is court language. John is saying, 'This is not just a set of nice stories. Many others and I were eyewitnesses. We testify to it. We really saw him. He really lived; he really died; he really rose from the dead.' If Christmas is just a nice legend, in a sense you are on your own. But if Christmas is true - and John says that it absolutely is true - then you can be saved by grace." (Tim Keller, Hidden Christmas [New York, New York: Viking, 2016], 21-2, 132-3)
See here for a collection of our resources on Christmas apologetic issues.