How long is a year on each planet?
A planet's year is the time it takes to go once around the Sun. The further out a planet is, the longer its path and the slower it travels, so years on the outer planets last a lifetime or more.
| Planet | One year lasts |
|---|---|
| Mercury | 88 Earth days |
| Venus | 225 Earth days |
| Earth | 365.25 days |
| Mars | 687 Earth days (1.88 years) |
| Jupiter | 11.9 Earth years |
| Saturn | 29.5 Earth years |
| Uranus | 84 Earth years |
| Neptune | 164.8 Earth years |
| Pluto (dwarf planet) | 248 Earth years |
How your age on Mars is worked out
Take the number of Earth days you've been alive and divide it by the length of that planet's year in Earth days. A 30-year-old has lived about 10,957 days. Divide by 687 and you get 15.9, so they're nearly 16 on Mars.
| Age on Earth | Age on Mars |
|---|---|
| 20 | 10.6 |
| 30 | 15.9 |
| 40 | 21.3 |
| 50 | 26.6 |
Days on Mars
A Martian day, called a sol, lasts 24 hours 39 minutes 35 seconds, only a little longer than ours. So on Mars you'd have roughly half as many birthdays but almost as many days. Mars is tilted on its axis by about 25 degrees, close to Earth's 23.4, so it has seasons too, each lasting roughly twice as long as ours.
Birthdays elsewhere in the solar system
On Mercury you'd celebrate a birthday about every three months and be over four times your Earth age. On Jupiter, birthdays come round about every 12 years. Nobody has ever lived long enough to turn one on Neptune.
Questions
Which planet would make me oldest?
Mercury, which races around the Sun in 88 days. Your Mercury age is about 4.15 times your Earth age.
Why is Earth not exactly my age?
The Earth figure counts complete trips around the Sun, which take 365.256 days. Calendar years average 365.2425 days, so the two drift apart very slowly, by about a day every 75 years.
Is my birth date stored anywhere?
Only in your own browser, so you don't have to type it again on other pages of this site. It's never sent to us or anyone else.