Age on other planets
Neptune takes 164.8 Earth years to orbit the Sun, so it has completed exactly one orbit since its discovery in 1846 — that anniversary fell in 2011. No human has ever been one Neptunian year old, and nobody ever will be. Mercury is the opposite extreme: a year there is 88 days, so a ten-year-old is already past forty.
A year is one orbit, and orbits vary enormously. Mercury takes 88 Earth days, Mars 687, and Neptune nearly 165 Earth years — so a 36-year-old is 149 on Mercury, 19 on Mars and one fifth of a year old on Neptune.
How to find your age elsewhere
Days are stranger than years. A day on Venus lasts 243 Earth days — longer than its 225-day year — so a Venusian day is longer than a Venusian year, and the Sun rises in the west because Venus rotates backwards. Mercury has a 3:2 resonance between its rotation and orbit, giving it a solar day of 176 Earth days, or two Mercurian years. Orbital periods are the tidy part of this comparison.
Questions
687 Earth days, or about 1.88 Earth years.