How long is a day on Venus? A planet's day is the time it takes the planet to rotate or spin once on its axis. Venus rotates much more slowly than Earth does, so a day on Venus is much longer than a day on Earth. A day on Venus lasts for 243 Earth days or 5,832 hours! A day on Earth is 23.943 hours. Venus also rotates backwards compared to the Earth and most of the other planets.