Earth years are only one way to count another trip around a star.
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About this tool
How it works
Each age divides elapsed Earth days by the planet's approximate orbital period. Results are educational approximations rather than astronomical event predictions.
Example
An Earth age of 30 is roughly 124.5 Mercury years but only about 2.5 Jupiter years.
Private by default
The calculation or transformation happens in this browser. There is no account, and the values you enter are not sent to NaughtyBear Labs.
How to use Planet Birthday
- Enter an Earth birth date.
- Compare your approximate age using each planet’s orbital period.
- Explore the estimated date of the next planetary birthday and share an interesting result.
Common questions
- Why is my age different on every planet?
- A planetary year is one orbit around the Sun, and each planet takes a different amount of Earth time to complete an orbit.
- Are the dates astronomically exact?
- No. The app uses approximate orbital periods for an educational calculation rather than predicting precise astronomical positions.