<P> Earth rotates once in about 24 hours with respect to the Sun , but once every 23 hours , 56 minutes , and 4 seconds with respect to the stars ( see below ) . Earth 's rotation is slowing slightly with time ; thus , a day was shorter in the past . This is due to the tidal effects the Moon has on Earth 's rotation . Atomic clocks show that a modern day is longer by about 1.7 milliseconds than a century ago , slowly increasing the rate at which UTC is adjusted by leap seconds . Analysis of historical astronomical records shows a slowing trend of 2.3 milliseconds per century since the 8th century BC E . </P>
how long is one full rotation of the earth
about 24 hours