Our daily cycle is set at 24 hours, but this period has no fundamental reason for its existence. In fact, it’s different from the past and will be different in the future. The Moon’s formation about 60-175 million years ago impacted Earth’s rotation, making a day on an Earth-like exoplanet potentially very different.
Recent computer simulations suggest that if there were no Moon, the Earth might have spun up to just four hours long after a massive collision with Mars-size object Theia. As the Moon receded, it transferred angular momentum to the Earth’s spin, lengthening the day by about 16 hours over time.
The energy released during Theia’s impact melted Earth’s surface into a magma ocean, causing temperatures of around 2,300 degrees Kelvin (3,680°F). It took hundreds of millions of years for the planet to cool and allow life as we know it to emerge. The duration of a day has varied significantly over time, from about 10 hours to the current 24 hours.
Changes in Earth’s rotation occur due to several factors, including gravitational influences from the Moon and Sun, climate warming, seismic activity, and even human activities like GPS satellite launches. A catastrophic event in a billion years could potentially increase the duration of a day by just over a tenth of a second.
Source: https://avi-loeb.medium.com/history-of-the-duration-of-a-day-on-earth-ff975be36132