Age on other Planets

Want to melt those years away?

Travel to an outer planet!

Fill in your birthdate below in the space indicated. (Note you must enter the year as a 4-digit number!)

Click on the "Calculate" button.

Notice that your age on other worlds will automatically fill in. Notice that Your age is different on the different worlds. Notice that your age in "days" varies wildly.

Notice when your next birthday on each world will be. The date given is an "earth date".

WHAT IS GOING ON?

The Days (And Years) Of Our Lives

Looking at the numbers above, you'll immediately notice that you are different ages on the different planets. This brings up the question of how we define the time intervals we measure. What is a day? What is a year?

The earth is in motion. Actually, several different motions all at once. There are two that specifically interest us. First, the earth rotates on its axis, like a spinning top. Second, the earth revolves around the sun, like a tetherball at the end of a string going around the center pole.
The top-like rotation of the earth on its axis is how we define the day. The time it takes the earth to rotate from noon until the next noon we define as one day. We further divide this period of time into 24 hours, each of which is divided into 60 minutes, each of which is broken into 60 seconds. There are no rules that govern the rotation rates of the planets, it all depends on how much "spin" was in the original material that went into forming each one. Giant Jupiter has lots of spin, turning once on its axis every 10 hours, while Venus takes 243 days to spin once.
The revolution of the earth around the sun is how we define the year. A year is the time it takes the earth to make one revolution - a little over 365 days.
We all learn in grade school that the planets move at differing rates around the sun. While earth takes 365 days to make one circuit, the closest planet, Mercury, takes only 88 days. Poor, ponderous, and distant Pluto takes a whopping 248 years for one revolution. Below is a table with the rotation rates and revolution rates of all the planets.

Planet	Moons	Rotation Period	Revolution Period	Temp (°F)
Mercury	0	58.65 days (58 days 16 hrs)	87.970 days (0.2 years)	333
Venus	0	- 243.01 days (- 243 days 26 mins)	224.70 days (0.6 years)	867
Earth	1	0.997 days (23 hrs 56 mins)	365.256* days (1 year)	59
Moon	0	27.322 days (655 hrs 58 mins)	365.256 days (1 year)	-4
Mars	2	1.026 days (24 hrs 36 mins)	686.980 days(1.9 years)	-85
Jupiter	95	0.410 days (9 hrs 55 minsw)	4332.82 days (11.9 years)	-166
Saturn	274	0.426 days (10 hrs 33 mins)	10755.70 days (29.5 years)	-220
Uranus	28	- 0.746 days (- 17 hrs 14 mins)	30687.15 days (84 years)	-320
Neptune	16	0.718 days (16 hrs 6.6 mins)	60190.03 days (164.8 years)	-330
Dwarf PLanets
Pluto	5	- 6.4 days (- 6 days 9 hs 17.6 mins)	90465 days (247.7 years)	-375
Ceres	0	0.37809 days (9 hrs 4 mins)	1678.64 days (4.599 years)	-149.17
Haumea	2	0.1631458 days (3 hrs 56 mins)	104171 days (285.4 years)	-369.4
Makemake	0	0.9511083 days (22 hrs 49 mins)	113106.2 days (309.88 years)	-410
Eris	4	-15.786 days (-15 days 18 hrs 52 mins)	203305 days (557 years)	-382
		Negative values of rotation period indicate that the planet rotates in the direction opposite to that in which it orbits the Sun. This is called retrograde rotation.	* The length of the Earth's orbital period, although called a "year" in the discussion, is not the same as the calendar (or tropical) year, which is about 20 minutes shorter than the orbital period due to the precession of the Equinoxes, and is about 365.244 days.

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Most recent revision July 12, 2025 08:38:31 AM

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Your Age On Other Worlds

Want to melt those years away?

MERCURY

VENUS

EARTH

MARS

JUPITER

SATURN

URANUS

NEPTUNE

PLUTO

WHAT IS GOING ON?

The Days (And Years) Of Our Lives

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