What this calculator does
This tool compares your age on Earth with your age on
other planets in the Solar System. You can either enter your current
age in Earth years, or let the calculator compute it from your
date of birth and an as-of date
(usually today).
Using the orbital period of each planet (how long it takes to complete
one orbit around the Sun, measured in Earth years), the calculator
converts your Earth age into “planet years” for:
- Mercury
- Venus
- Earth (reference)
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
How to use the age-on-planets tool
-
If you already know your age in years (for example 25.5), type it into
“Your age on Earth (years)”.
-
If you prefer, leave that field empty and instead select your
date of birth and an as-of date
(usually today). You can click “Use today” to fill the as-of date.
-
Click “Calculate”. The calculator will show:
- Your age on Earth in years (and, if available, in years–months–days).
- Your age on each planet, in planet years.
- The orbital period of each planet, expressed in Earth years.
-
Use the table to compare how “old” you would be on each world, knowing that
the length of a year depends on the planet.
How the calculator computes your ages
First, the tool needs your age in Earth years.
-
If you enter your age directly, that number is used as
\( A_{\oplus} \), your Earth age in years.
-
If you provide date of birth and as-of date, the calculator finds the time
difference in days and converts it to Earth years using an average year
length of \(365.25\) days.
Symbolically,
\[
\Delta t_{\text{days}}
= \frac{t_{\text{ref}} - t_{\text{birth}}}{86\,400\,000},
\]
where \(t_{\text{birth}}\) and \(t_{\text{ref}}\) are the birth and
reference dates in milliseconds, and \(86\,400\,000\) is the number
of milliseconds in one day.
\[
A_{\oplus} = \frac{\Delta t_{\text{days}}}{365.25}.
\]
Orbital periods and planet years
Each planet has its own orbital period around the Sun, expressed in
Earth years. For example, a common set of approximate values is:
\[
\begin{aligned}
T_{\text{Mercury}} &\approx 0.2408467 \\
T_{\text{Venus}} &\approx 0.6151973 \\
T_{\text{Earth}} &= 1.0000000 \\
T_{\text{Mars}} &\approx 1.8808158 \\
T_{\text{Jupiter}} &\approx 11.862615 \\
T_{\text{Saturn}} &\approx 29.447498 \\
T_{\text{Uranus}} &\approx 84.016846 \\
T_{\text{Neptune}} &\approx 164.79132
\end{aligned}
\]
If your age in Earth years is \( A_{\oplus} \), then your age on a given
planet is obtained by dividing by that planet’s orbital period:
\[
A_{\text{planet}} = \frac{A_{\oplus}}{T_{\text{planet}}}.
\]
For instance, your age in Mars years is
\[
A_{\text{Mars}} = \frac{A_{\oplus}}{T_{\text{Mars}}}
= \frac{A_{\oplus}}{1.8808158}.
\]
How to interpret the results
The output table lists, for each planet:
- The name of the planet.
- Your age in that planet’s years (rounded to two decimal places).
- The orbital period of the planet in Earth years.
If a planet’s year is shorter than an Earth year (for example Mercury),
you will appear older in that planet’s years, because
more planet years fit into the same Earth time. If a planet’s year is
much longer than an Earth year (for example Neptune), you will appear
younger in planet years.
This does not change how you age biologically. It simply illustrates
that the concept of “one year” depends on where you are in the Solar
System, because it is tied to the orbital period of a particular planet.
