The Lord is mentioned in the Constitution, you are simply unaware of that indisputable fact.I assume you mean the date. That's really grasping at straws. It was the common dating convention of the era. When the federal government uses day names such as Monday or Friday, is it endorsing the pagan faiths those names came from? The Quakers began using numbers to avoid those names, this could have been adopted by the government as well.
If these precise men had wanted to endorse God or Christianity in the Constitution certainly they wouldn't have done so merely in the date.
-Eric