Wikipedia describes the standard explanation for the origin of the earth’s rotation
"It is theorized that Earth formed as part of the birth of the Solar System: what eventually became the solar system initially existed as a large, rotating cloud of dust, rocks, and gas. It was composed of hydrogen and helium produced in the Big Bang, as well as heavier elements ejected by supernovas. Then, as one theory suggests, about 4.6 billion years ago a nearby star was destroyed in a supernova and the explosion sent a shock wave through the solar nebula, causing it to gain angular momentum. As the rotating cloud flattened out, some of the gas and dust clustered together due to gravity (eventually becoming planets). Because the initial angular momentum needed to be conserved, the clustered mass started rotating faster (much in the same way an ice skater rotates quicker with his/her arms "clustered" closely to his/her body). The current rotation period of the Earth is the result of this initial rotation and other factors, including tidal friction and possibly the giant impact hypothesis".
There is one small detail which is overlooked – the earth accelerates and decelerates according to sunspot activity and the solar cycle necessitating the resetting of the atomic clocks, from time to time. Right now it’s rotation has settled down but there are some web sites which make much of the idea that because the earth’s rotation is inertial, it must eventually run down, pointing to a very young earth.
Unfortunately this isn’t the case, because the earth rotates for a quite different reason – the Faraday Motor effect.
The electric currents enter at the poles and the rotation as shown in the above diagram.
NASA has discovered that the Earth’s ionosphere is connected to the Sun by enormous magnetic flux ropes pumping enormous amounts of electrical energy into the earth. These currents power the Earth Faraday motor and variations in the solar currents will cause variations in the earth’s rotation as a consequence.
"The electromotive power is deposited mostly in the upper atmosphere at mid to low latitudes and gives rise to fast upper atmosphere winds and even "super rotation." That is, the wind races around the planet faster than the planet turns. It is a phenomenon observed on Venus and Titan and remains unexplained by atmospheric physics, which relies on solar heating. It is the cause of the extraordinary winds on the gas giant planets in the outer solar system, where solar heating is weak. It has implications for the jet streams and weather patterns on Earth as well. Notably, the polar current streams take the form of twin Birkeland current filaments, which give rise to the enigmatic "double vortexes" seen at the poles of Venus. It is apparent that electrical energy from space doesn’t merely light up auroras. It has a profound influence on upper atmosphere winds and storms. An expert on the dynamics of planetary atmospheres, F. W. Taylor, has admitted, "the absence of viable theories which can be tested, or in this case [Venusian polar vortex] any theory at all, leaves us uncomfortably in doubt as to our basic ability to understand even gross features of planetary atmospheric circulations." Meanwhile, electrical energy appears nowhere in any climate model."