The Motion of the Earth
From: http://www.tigerwave.com/spaceflight/EarthMotion.htm
" The Earth spins around an axis. The Earth takes (a bit more than) one day to go around once. This axis is pointing off somewhere in space. This axis (mostly) doesn¡¯t move. At the same time, the Earth is orbiting the Sun. It takes (a bit more than) one year to go around once. The plane of the Earth¡¯s orbit (mostly) doesn¡¯t move. The spin axis of the Earth¡¯s daily rotation is not perpendicular to the plane of the Earth¡¯s orbit.It is tilted (approximately) 23.4 degrees. The angle of tilt (mostly) doesn¡¯t change. "
Earth does not spin perpendicular to the plane it is tilted, the reason earth is tilted is because it got hit by meteoroids and other stuff when the planets first formed.
Also it takes about 24 hours for one period of earth rotate. From that we get sunlight, half of our days.