Frequently Asked Questions

Enter your birth date and the tool computes your exact age in days, then divides that by each planet's orbital period — the time it takes to complete one orbit — to find your age in that planet's years. It also shows how long each planet's year is in Earth days or years, and the days remaining until your next "planetary birthday" on every world. Switch between Our Solar System and the TRAPPIST-1 System at any time; your birth date is preserved.

A "year" is defined as one complete orbit of the Sun — and each planet takes a different amount of time to complete that orbit. Mercury orbits in just 88 Earth days, so a Mercury year is very short and you'd celebrate far more Mercury birthdays than Earth birthdays in the same lifetime. Neptune takes 165 Earth years per orbit, so you've barely completed a fraction of a Neptune year. The same elapsed time equals different numbers of "years" depending on the planet.

Yes, completely free with no sign-up, no downloads, and no limits. Enter any birth date as many times as you like, across both planetary systems, on any device.

Yes. Switch to the TRAPPIST-1 System tab to see your age on seven real exoplanets orbiting a star about 39 light-years from Earth. Their orbital periods range from just 1.5 to 18.8 Earth days, so your age in TRAPPIST-1 planet-years will be in the thousands or tens of thousands. The periods shown are real measured values from transit photometry — not guesses.

TRAPPIST-1 planets orbit their host star in only a few Earth days — TRAPPIST-1 b completes a full orbit in about 1.5 days. So even a 30-year-old has lived through over 7,000 of those orbits, making them over 7,000 "years" old by TRAPPIST-1 b standards. It's a direct consequence of very short orbital periods: the same number of elapsed days divides into many more "years." The number is real — just an unusual way to frame time.

In Our Solar System: all eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) plus Pluto — nine bodies in total. Earth is shown as your reference point so you can confirm the result against your known age. In the TRAPPIST-1 System: all seven known planets (b through h), all of which have precisely measured orbital periods from transit photometry.

The tool divides your elapsed days by the planet's orbital period to find how many complete orbits you've done. The fractional part shows how far you are through your current orbit. Subtracting from the full period gives the remaining days — shown rounded to the nearest whole day. "Today!" appears when you're within half a day of completing that planet's current orbit.

The tool uses real measured orbital periods from the NASA Planetary Fact Sheet (Solar System) and Agol et al. 2021 (TRAPPIST-1). When you enter a birth date, elapsed days are computed exactly from timestamps, handling leap years automatically. The Earth-age fallback uses 365.25 days per year, which is a close approximation. The results are as accurate as the source data — this is real science, presented as a fun comparison.

No. Your birth date is processed entirely in your browser and is never sent to a server or stored anywhere. Close the tab and everything is gone.

Yes, fully responsive. On mobile, the date input uses the device's native date picker for easy entry, and the results grid adapts to a two-column layout so everything fits without horizontal scrolling. Tap targets are large enough for comfortable use on small screens.