Earth's Days Were Only 19 Hours Long for a Billion Years

A recent study by researchers from China and Germany has found that during the Proterozoic Epoch, a geological period that lasted from 2.5 billion years to 541 million years ago, an average day lasted about 19 hours for one billion years. This demonstrates that rather than gradually increasing over time, the length of a day on Earth remained constant for an extended period. The study also supports the idea that longer days were needed before photosynthetic bacteria could produce enough oxygen to reach modern atmospheric levels.