1. Rotational Period (how long it takes to spin once):
* Mercury: 58.6 Earth days
* Venus: 243 Earth days (and it rotates backwards!)
* Earth: 23.93 hours
* Mars: 24.6 hours
* Jupiter: 9.9 hours
* Saturn: 10.7 hours
* Uranus: 17.2 hours (rotates on its side)
* Neptune: 16 hours
2. Sidereal Day (time between seeing the same star in the same position):
* Mercury: 58.6 Earth days (same as the rotational period)
* Venus: 116.8 Earth days (2x the rotational period, because Venus rotates very slowly)
* Earth: 23 hours and 56 minutes
* Mars: 24 hours and 37 minutes
* Jupiter: 9 hours and 55 minutes
* Saturn: 10 hours and 45 minutes
* Uranus: 17 hours and 14 minutes
* Neptune: 16 hours and 6 minutes
Why the Difference?
The difference between rotational period and sidereal day is due to the planets' orbits around the Sun. As a planet rotates, it's also moving around the Sun. The sidereal day takes into account this orbital motion.
Let me know if you'd like more details about any particular planet's day length!
