How planetary age is calculated
Every planet orbits the Sun at a different speed. A "year" on any planet is simply the time it takes that planet to complete one orbit around the Sun. Your age on a planet is the number of times that planet has orbited the Sun since you were born.
Formula
f
planetary_age = earth_age_in_days ÷ planet_orbital_period_in_days
Earth age in days = days since birth. Orbital period for each planet is from NASA planetary fact sheets.
Earth age in days = days since birth. Orbital period for each planet is from NASA planetary fact sheets.
ex
Example — Mars: Earth age of 30 years = 10,957 days. Mars orbital period = 686.97 Earth days. Martian age = 10,957 ÷ 686.97 = 15.95 Martian years.
Planetary Orbital Periods
| Planet | Orbital Period (Earth days) | Orbital Period (Earth years) |
|---|---|---|
| ☿ Mercury | 87.97 days | 0.241 years |
| ♀ Venus | 224.70 days | 0.615 years |
| 🌍 Earth | 365.25 days | 1.000 year |
| ♂ Mars | 686.97 days | 1.881 years |
| ♃ Jupiter | 4,332.59 days | 11.862 years |
| ♄ Saturn | 10,759.22 days | 29.457 years |
| ♅ Uranus | 30,688.50 days | 84.011 years |
| ♆ Neptune | 60,195.00 days | 164.79 years |
Source: NASA Planetary Fact Sheets (nssdc.gsfc.nasa.gov).
Interesting Facts
- On Mercury, a year is only 88 Earth days — shorter than Mercury's own day (58.6 Earth days for one rotation). You'd have a birthday every 3 months!
- On Venus, a day is actually longer than a year — Venus rotates so slowly that its year (225 days) is shorter than one Venusian day (243 Earth days).
- On Saturn, someone born in 1996 would be having their first Saturnian birthday around 2026. Saturn's year is 29.5 Earth years long.
- On Neptune, the planet has only completed roughly one orbit since it was discovered in 1846. Neptune's first "year" ended around 2011.
- On Jupiter, a 35-year-old Earth person is less than 3 years old in Jovian years.