The length of a day on Jupiter is 9 hours and 56 minutes. Jupiter rotates the fastest of all the planets in the solar system.
Jupiter's speedy rotation accounts for its equatorial bulge, which anyone with a telescope can see clearly from Earth. The rotation also accounts for Jupiter's turbulent weather system. Jupiter is a mostly gaseous planet, with an upper atmosphere that rotates at a different rate than the lower. One result is the Great Red Spot, a more than 100-year-old storm system that's bigger than two Earths. The Great Red Spot has wind speeds many times faster than any terrestrial hurricane.