The last leaves on a white oak.

So the last leaves fell off the white oak tree in my backyard today. I am telling you this because my father always told me (and his father always told him, etc.) the leaves won't fall off a white oak tree until after the LAST frost of winter. I can only think of one time in my entire life when this is wrong. Last weekend it snowed here, and it NEVER snows here. Has anyone else heard of this?