27 Feb '13 17:09>
Originally posted by PenguinThen God said, “Let there be lights in the firmament of the heavens to divide the day from the night; and let them be for signs and seasons, and for days and years;...So the evening and the morning were the fourth day.
But the sun and the moon were not created until day 4, and man not until day 6. It really does not specify how long each day took before day 4. It doesn't really specify the length of any of the days at all.
--- Penguin
(Genesis 1:14,19 NKJV)
The above scripture is what you are referring to apparently. These lights refer mainly to the Sun and the Moon that God made for many reasons and a couple of these reasons is quoted above. Now, by using the sun and the moon, man would also be able to tell time like God. Notice that one should understand that this was made by God for man as a time keeper.
So you might ask why God did not just wait until He had made man? The answer is that there were other purposes for the Sun, like providing light and energy for the plant life that God had just created on the third day. Although, it may all seem mad to you, there is a logic to it all, if we really think about it. I believe God must have put much thought and planning into all this before He started this creating of the physical universe, because He knew it had to be done quickly to work.
The main question you wanted to know was how God knew how long the first 3 days were, so He could tell Moses, since the Sun and moon had not been created yet? Here you are assuming that the One that made the time keeper for man also need the same time keeper. There is no mention of how God knew anything, we are apparently just to take it for granted that God knew all He needed to know to do all this and somehow he synchronized the time it took for the first 3 days with the time keeper He made for man on the 4th day. It is a matter of faith to believe what God says as the eyewitness.