I think the Earth's rotation has increased slightly.

I recall reading a sleep study done on circadian rhythms. The circadian rhythm is the natural, internal clock that guides our day to day habits. People sealed in rooms with no windows, clocks, or any time reference were studied for many days. Their internal clocks took over and told them when to sleep, and when to wake. It told them when to ask for food, and when to do any number of daily routine activities.

The study showed that on average, the natural circadian rhythm of humans is on a 25 hour cycle. We lose an hour every day, compared to the natural state our bodies want to live in. If the rotation of the Earth would slow down just one hour to fit 25 hours into the day, who knows what improvements to our lives that would incur.