Days have been getting longer by about 0.0016 seconds each century.
This is because of the rotation of the earth. As the Earth rotates beneath the tidal bulges, it attempts to drag the bulges along with it. A large amount of friction is produced which slows down the Earth’s spin.
Over the course of time this friction can have a noticeable effect. Growth rings in ancient corals about 400 hundred million years old, show that the day was only 22 hours long and, therefore, there were over 400 days in a year! Eventually the Earth’s rotation will slow down to where it keeps only one face toward the Moon.