A year on each planet is the time it takes to complete one orbit around the Sun. Because orbital periods differ wildly, your age changes dramatically from planet to planet. Enter your birth date to see your age across the Solar System.
Your age on another planet is simply your Earth age divided by that planet's orbital period in Earth years. Mercury races round the Sun every 88 Earth days, so you rack up Mercury years quickly; Neptune takes nearly 165 Earth years to complete one orbit, so a Neptune year is a long wait.
We measure your Earth age precisely from your date of birth to today (accounting for leap years), then divide by each planet's orbital period to give a decimal age on every planet in the Solar System.
The formula is: age_on_planet = earth_age_in_years / orbital_period_in_earth_years.