No, saying they 'just happened' implies a process. They just *are*, for all of space and time.
Time existed long before humans. It is a fundamental aspect of our universe. And causality is tightly tied with the notion of time. Your ramble about God is rather beside the point. Calendars are how *we* measure time, but if there is change, there is time. The earth spins, stars emit energy, atoms interact: all these are indications of time.
But one aspect here is that you are thinking of time as a separate thing. It is part of the universe. Just like latitude and longitude are part of the geometry of the Earth, space and time are part of the geometry of our universe. And just like the Earth is curved, spacetime can be curved. And that curvature produces the effects we call gravity.
But more to the point, if we consider the universe to be *all* of space and *all* of time, as a single thing, then it just simply exists. It didn't 'come from' anywhere because it *is* everything. It isn't caused because all causality is *within* it. It didn't come into being because it *is* all that is and 'to come into being' implies time, which is part of it.