Fair enough. I could explain further, but you’re right, it is academic and derailing the intention of the thread. If it helps, I think I understand your point.
What’s your opinion on Alexander the Great? Do you feel there are no historical records about him?
Sorry, it has been a long time since catholic high school, but I thought the story of Jesus’ birth was in all 4 gospels, but obviously it isn’t.
I don’t see history as quantized. Everything that happens is the confluence of events that preceded it. The influence of Christianity couldn’t have happened without Paul. Paul wouldn’t have been proselytizing without Christianity having happened. Christianity wouldn’t have happened without Jesus, and Jesus started with his birth. Thus, the significant even is Jesus’ birth. At least to those who view the influence of Christianity to be the most significant historical event.
… have a discussion thread on this subject that does not devolve into a sidebar discussion about some facet of Christianity?
That would be momentous. Not as momentous as the cancellation of Hee Haw, but pretty damned significant.
The funny thing is, it’s not the birth of Jesus that’s considered so unusual but his resurrection. Without that, you got nothin’.
Anyway…
Since “event” indicates an act, possibly spanning a length of time and comprised of smaller “events” (like WW2 is an “event”), and limiting my answer to something in the historical record (meaning that writing, agriculture, domestication, and other pre-historical events are out of the running), I think the answer is, easily…
The Industrial Revolution
This is a vast subject. It’s not even easy to see how big it is. Within a century, “laid back” and slowly changing societies of landed farmers, peasants, burghers, coolies, castes, and others became time-sensitive societies of machine operators, time-clock punchers, management specialists, engineers, and workers. The industrial tide has proved irresistible no matter the cultural origin of the peoples adopting it: European, Chinese, Japanese, African, Indian, more… regardless of where you are on the world, the lesson is simple: Industrialize or die.
It is impossible for humanity today to understand or even visualize a pre-industrial world. You can’t look to the movies for examples, as all the props are machine made. You can’t read pre-industrial books and writings without the assumptions of a post-industrial society clouding your understanding. The IR is a giant wall, blocking modern humanity from the vast majority of its history, and even in societies not as “advanced” as those of the developed nations, the IR has wrought unfathomable changes to their way of life.
The closest competitor is the Scientific Revolution, but that hasn’t had such a personal impact upon as many people as the Industrial Revolution had. Just ask 19th-century Africans who saw their continent divided among industrialized powers, who fought machine guns with spears and arrows. They might not have understood the science behind guns (or that there was even such a thing as “science behind guns”), but they definitely understood that the people with the machines were winning. Same thing with Japan. And China. And Russia. And everywhere else.
As a world-shaper, it has no competitor. None.
All imho, of course… 
No.