That is exactly the point - It was six of GOD's days - not six of ours.
but God doesnt have days -- He is outside time. it could only be days in relation to creation. plus, the Scripture says that the Jews kept the Sabbath bc of how God created.
i think this quote applies here:
St. Ambrose writes:
Moses "spoke to God the Most High, not in a vision nor in dreams, but mouth to mouth" (Numbers 12:6-8). Plainly and clearly, not by figures nor by riddles, there was bestowed on him the gift of the Divine presence. And so Moses opened his mouth and uttered what the Lord spoke within him, according to the promise He made to him when He directed him to go to King Pharaoh: "Go therefore and I will open thy mouth and instruct thee what thou shouldest speak" (Ex. 4:12). For, if he had already accepted from God what he should say concerning the liberation of the people, how much more should you accept what He should say concerning heaven? Therefore, "not in the persuasive words of wisdom," not in philosophical fallacies, "but in the demonstration of the Spirit and power" (1 Cor. 2:4), he has ventured to say as if he were a witness of the Divine work: "In the beginning God created heaven and earth."
also, St. Basil writes:
We are proposing to examine the structure of the world and to contemplate the whole universe, not from the wisdom of the world, but from what God taught His servant when He spoke to him in person and without riddles.
i think its pretty fair to say that if God were speaking to Moses about days, but meaning God days, that could be considered speaking iwith figures and in a riddle.
also, St. John Chrysostom says:
The blessed Moses, instructed by the Spirit of God, teaches us with such detail ... so that we might clearly know both the order and the way of the creation of each thing. If God had not been concerned for our salvation and had not guided the tongue of the Prophet, it would have been sufficient to say that God created the heaven, and the earth, and the sea, and living creatures, without indicating either the order of the days or what was created earlier and what later.... But he distinguishes so clearly both the order of creation and the number of days, and instructs us about everything with great condescension, in order that we, coming to know the whole truth, would no longer heed the false teachings of those who speak of everything according to their own reasonings, but might comprehend the unutterable power of our Creator.
if the days are not man's days but rather God's days then it cannot be said that God distinguishes clearly the number of days.