We call the time it takes for our planet to rotate completely around its own axis a day. 300 million years ago it was 21 hours, and the year lasted 450 days. But today we have 24-hour days and 365-day years.
However, the time spent on one Earth's rotation fluctuates. On the one hand, the time it takes for the Earth to rotate around its axis is different by a range of milliseconds each day of the year, due to the impact of weather patterns, ocean currents and other factors. But also Richard Holmes, from the University of Liverpool in the United Kingdom, and Olivier de Viron, from the University of Paris (France) have identified that there are periodic long-term changes. Specifically, every 5.9 years the planet goes through a period of several months during which the length of each day is greater or less than what is considered "normal" . Although the causes are not yet clear, scientists suspect that it is related to phenomena that take place at the boundary between the core and the Earth's mantle and to changes in the magnetic field generated in the center of the Earth.
