And God created the universe in 6 days, but in order to give us a nice sky full of beautiful shiny stars, he decided to simulate the light as though as it was coming from thousands, millions and billions of years ago in the past. This was necessary because the speed of light is so fast that in 6 days there would be no chances for us to see anything, not even the light from our closest star, excepting our own sun. We would not be able to see the Milky Way as we see it today, not even in 6 thousand years.
However, God did his job so well that there is no way for anybody to find any hint of crack in the simulation. Unfortunately, this implies that humans will never be able to prove that the universe was created in 6 days, no matter how hard they could try.