A day on Jupiter lasts the equivalent of nine hours and 55 minutes on Earth. The length of a day is determined by how long it takes a planet to complete a rotation. Despite the fact that Jupiter is the largest planet in the solar system, it rotates the fastest.
A year on Jupiter is equivalent to 11.86 years on Earth. The length of a year is determined by how long it takes a planet to orbit the sun. Jupiter is the fifth planet from the sun and, according to About.com, the brightest object in the sky visible from Earth after the sun, the moon and Venus.