About

Time is not a universal constant when measured by celestial cycles. A year is defined by a single complete orbit of a planet around its host star. On Earth, this duration is approximately 365.25 days. However, orbital periods vary drastically across the cosmos due to Kepler’s laws of planetary motion. A planet closer to the sun moves faster and has a shorter path, resulting in a significantly shorter year.

This tool calculates your age based on the unique orbital periods of planets, dwarf planets, and notable exoplanets. It determines the total number of Earth days you have been alive and divides this by the orbital period of the target body. This calculation is essential for science fiction writers ensuring chronological consistency, educators demonstrating solar system scale, or astronomy enthusiasts seeking a new perspective on time.

Accuracy is maintained by using precise sidereal orbital periods for each body. The tool differentiates between terrestrial planets, gas giants, and distant Trans-Neptunian Objects, providing a comprehensive overview of your existence across the galaxy.

Formulas

The calculation of planetary age relies on the ratio of Earth’s orbital period to the target planet’s orbital period. First, we determine the total time the subject has been alive in Earth days.

talive = Datecurrent − Datebirth

Once the total days talive is known, the age on a specific celestial body Aplanet is calculated using its orbital period Pplanet.

AplanetYears = talivePplanet

To find the date of the next birthday on that planet, we calculate the remaining days to complete the current orbit and project that forward from the current date.

dnext = Pplanet − (talive mod Pplanet)

Reference Data

Celestial Body	Classification	Orbital Period (Earth Days)	Years per Earth Year
Mercury	Terrestrial Planet	87.97	4.15
Venus	Terrestrial Planet	224.70	1.62
Earth	Terrestrial Planet	365.26	1.00
Mars	Terrestrial Planet	686.98	0.53
Ceres	Dwarf Planet	1,681.63	0.22
Jupiter	Gas Giant	4,332.59	0.08
Saturn	Gas Giant	10,759.22	0.03
Uranus	Ice Giant	30,688.50	0.01
Neptune	Ice Giant	60,182.00	0.006
Pluto	Dwarf Planet	90,560.00	0.004
Haumea	Dwarf Planet	103,468.00	0.0035
Eris	Dwarf Planet	203,830.00	0.0018
Sedna	Trans-Neptunian	4,164,150.00	0.00008
Proxima Centauri b	Exoplanet	11.19	32.65
TRAPPIST-1e	Exoplanet	6.10	59.88

Frequently Asked Questions

Mercury orbits the Sun much faster than Earth due to its proximity to the star. It completes one revolution (a year) in just 87.97 Earth days. Consequently, for every single Earth year that passes, Mercury completes approximately 4.15 orbits, increasing your age count on that planet more than four times faster.

Yes. The calculation derives the exact number of days between your birth date and the current date, which naturally includes any leap days (February 29th) that have occurred. The orbital periods used for other planets are averaged sidereal periods to ensure long-term accuracy.

A sidereal day is the time it takes for a planet to rotate once on its axis relative to the stars. A solar day is the time it takes for the Sun to appear in the same position in the sky. On Earth, these are similar (23h 56m vs 24h). On Venus, however, the rotation is so slow and retrograde that a solar day is significantly different from its sidereal rotation period. This tool calculates age based on Orbital Periods (Years), not daily rotation.

Exoplanets like Proxima Centauri b or TRAPPIST-1e orbit other stars. We include them to illustrate the vast diversity of time scales in the universe. For example, a year on TRAPPIST-1e is only 6.1 Earth days, meaning you would be thousands of years old if you lived there.

A year on Jupiter is defined by its orbit around the Sun, not its rotation or internal composition. Despite being a gas giant with no solid surface to stand on, it still follows Keplerian orbital mechanics. One Jovian year equals roughly 11.86 Earth years.