Hello, Ji52orclo. Actually, Earth's rotation has slowed down; quite a bit, actually. When Earth was first born, it spun around on its axis in just a few minutes. As time went on, the rotation slowed down. In fact, during the Age of Reptiles, in which dinosaurs reigned supreme, Earth was rotating faster than it is today. So the dinosaur's days would've been shorter than our days by a few minutes or more.

Way to go, Raptorguy! Just an addendum to your reply to Ji52orclo. That the Earth's rotation was indeed a touch faster than today, it was not such an abrupt change, or large enough change of time as to affect life to the point of extinction.