How old is a 30-year-old on Neptune?

About 0.18 Neptune years old

On Earth we count years by Earth's orbit (about 365 days).Neptune takes 60182 Earth days per orbit, so someone who has lived 30 Earth years has completed fewer full orbits — hence a different "age."

Neptune takes 165 Earth years to orbit the sun. It has only completed ONE orbit since its discovery in 1846!