A day on Earth was only 18 hours long 1.4 billion years ago
About 1.4 billion years ago, a day on Earth lasted 18 hours 41 minutes, partly because the Moon was closer, according to a US-based study. "As the Moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out," said a geoscientist explaining Earth's rotational period is getting longer than 24 hours.