It was once said that "time is nature's way of preventing the universe from happening all at once."

And it was also said that the universe can be viewed as a succession of three dimensional slices......each slice a moment in the fourth dimension: time.

And lastly, it was said that the universe did happen all at once if viewed from a four dimensional vantage point. We simply live in one of a series of moments in three dimensions.

So before I was born I didnt exist. After i was born I did exist. Granted the material that makes me existed before my birth, my conscious mind did not.

So viewed from a four dimensional vantage point, I existed and didn't exist at the same time. That is, if you believe in this philosophical outlook.