But Earth’s rotation could change by a millisecond — which is .001 seconds — or two every day. Also, the orbit of the moon can have an effect on how fast the Earth spins.

Until 2020, the shortest "length of day" ever recorded by atomic clocks was -1.05 ms, meaning that Earth completed one daily rotation in 1.05 milliseconds less than 86,400 seconds.

Over time, that adds up. Experts think that 200 million years from now, there will be 25 hours in a full day. The Earth's rotation will speed up for three days this summer. (photovideostock/Getty ...

But Earth’s rotation could change by a millisecond — which is .001 seconds — or two every day. Also, the orbit of the moon can have an effect on how fast the Earth spins.