Time in Celestial Objects: Table of Planets’ days and years [3] 

The relationship between days and years isn’t straightforward. They are both distinct measures, and it just happens that on Earth a year is equal to about 365 days.

Yet in fact, different celestial bodies have different shapes and orbits, and this results in each body having distinct definitions and measurements of time.

For example, Jupiter takes about 10 Earth hours to make a full spin, but takes 12 Earth years to make one revolution around the sun.

Saturn takes an almost equal time as Jupiter to make a spin, but takes more than twice as long to rotate around the sun.

Outer planets – Jupiter, Saturn, Uranus and Neptune – called “Jovian Planets”, are larger, more massive, and composed mostly of gas. They generally spin faster than the inner, rocky, denser planets – Mercury, Venus, Earth, and Mars – also called terrestrial planets. Jovian planets thus have shorter ‘Earth’ days than terrestrial planets.

Inversely, gaseous planets have longer planetary years than terrestrial planets, particularly due to their greater distance from the sun.

This greater distance also results in a weaker gravitational pull from the sun on the planet, causing the planet to rotate at a relatively slower speed.

The different spinning/rotational speeds of celestial bodies are mostly attributed to how the body was initially formed and the gravitational forces that surround it.

Similarly interesting is the phenomenon of the continuous movement of the body, which is explained with the concept of angular momentum.