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Calculating your Age on another Planet

Time on the Planets

The Earth spins once every 24 hours which gives us the length of the day. It also orbits around the Sun once every year, which is about 365 days. However, other planets spin and orbit at different speeds, so their days and years are different lengths.

To work out your age on other planets, you need to calculate how many Earth days you have been alive (being careful of leap years). You can then calculate how many days or years that would be on another planet by finding out how long that planet takes to spin or orbit.

If you want to work it out for yourself, you can find the lengths of spin (rotation) and orbit for all of the planets, in the following data sheet. Look at the Year Length and Day Length rows. You can then check your answers with the age calculator.

Planet Data Sheet show »« hide
Facts and FiguresMercuryVenus EarthMarsJupiter SaturnUranusNeptune
Orbital Distance (AU)10.380.72 1.01.525.2 9.4519.230.06
Radius (KM)2,4406,052 6,3783,39771,492 60,26825,55924,746
Mass (Earth Masses)20.0550.82 1.00.11318 95.214.517.1
Year Length
(Earth Days)
88225 365.2568711.9
Day Length
(Earth Days)
176117 0.430.750.67
Surface Gravity (g)30.380.91 1.00.382.34 0.930.921.12
Surface Temperature-200 to
400 °C
460 °C -80 to
50 °C
-150 to
20 °C
-110 °C -140 °C-190 °C-200 °C
Number of moons00 1263 602713
Notes: 1 1 AU (or Astronomical Unit) = 149,600,000 KM and is the mean distance from the Earth to the Sun
2 1 Earth Mass = 5,980,000,000,000,000,000,000,000 KG : 3 1 g = 9.8 m/s2