Age on another planet
Planet age = Earth age (years) ÷ planet's orbital period (in Earth years)
A "year" is one orbit of the Sun, and each planet takes a different time: Mercury 0.24, Mars 1.88, Jupiter 11.86, Neptune 164.8 Earth years. So you've completed far more Mercury years than Earth years — and barely any Neptune years.
A birthday on every world
Your age is really just how many times Earth has orbited the Sun since you were born. Every planet orbits at its own pace, so your age changes dramatically across the solar system: you'd be in the hundreds on speedy Mercury and not even one year old on distant Neptune. Enter your birth date to see them all.