1. The Orbital Ratio Equation
A planetary year corresponds to one complete heliocentric orbit around the Sun. The age on planet $P$ is inversely proportional to its orbital period.
Age(P) =
Earth Age (Sidereal Years)
Orbital Period T(P)
Where $T(P)$ is the planetary orbital period in Earth years. By Kepler's Third Law ($T^2 \propto a^3$), orbital period scales exponentially with semi-major axis distance $a$ from the Sun.