If you look at the night sky different times of the year you see different constellations. This change is due to the motion of the Earth in its orbit around the Sun. Each day a few stars are visible in the east that were not visible the night before. If you were to measure how much the sky "shifted" from one day to the next you would discover that it "shifts" approximately one degree per day. This should not be surprising because, if you think about it there are 365 days per year and 360 degrees in a circle. Anyway, the sky doesn't shift, it is another case ofapparent motion. The "shift" of the sky is really the motion of the earth around the sun.