In the first million years of the Earth's existence, the day lasted only four hours. From the very beginning, the Earth has been losing energy as it rotates around its axis, which translates into lower and lower rotational speed and longer days. In the early days of dinosaurs, the day lasted about 22 hours, and at the end of their existence, 66 million years ago, it lasted about 23 hours. We will reach 25 hours a day in about 200 million years.
