Figuring out someone's age on different planets. (Not homework!)

I promise this is not homework. I’ve been out of school for 25 years. :slight_smile:

No, this is rather embarrassingly related to an RPG I’m involved with. (Probably would’ve been better if I had pretended it was homework!)

Here’s the sitch. There’s a character who’s born on a planet outside our own solar system. Logically, this planet’s “years” are different in length from our own; it takes longer for her planet to revolve around its star than it does for Earth to revolve around the sun.

However, this character interacts with humans and is used to having to express age according to Earth’s timeframe.

An important milestone in this character’s life will occur when she reaches the age of 20 (on her planet), which I want to be equivalent to 25 Earth years.

Right now, she is 23 1/2 in Earth years. How old would she be on her planet?

I just can’t seem to wrap my head around the task of figuring out how many Earth days = 1 year on her planet. Too much Calculus! Or is it Algebra? Either way, I’m too crappy at math to figure out a formula for calculating this time/age discreprency.

The closest I could sorta come up with was 20n = 25(365). Is that right? Even if it is, how does that help me figure out her current age?


25/20 = 1.25. Her planet’s years are 25% longer than Earth years.

1.25 x 365 = 456. Her planet’s years are 456 Earth days long.

She is 23.5 x 365 Earth days old = 8,577 days.

8,577/456 = 18.8 years old on her planet.

Ignoring rounding and leap years.

You don’t need to bring 365 or days into it, necessarily. If 20 planet X years = 25 Earth years, then you can just multiply by 0.8 to get from earth years to planet X years, or by 1.25 to get from planet X years to earth years.

So 23.5 Earth years = 23.5 * 0.8 = 18.8 years on her planet.

And I think a year there would be around 456 (365 * 1.25) Earth days.

Does that help?

Sigh, Colibri showed his work first. :smiley:

Ah, but your solution is more elegant.:slight_smile:

Oh LOL, I was just trying to calculate this and I came up with this tortured version:

There are 9125 (Earth) days in 25 years.

Divide that by 20 instead of 25 and I get 456.25. So there are 456.25 Earth days in one of her planet’s years.

Next, I take 23.5 (her current Earth age) and multiply that by 365 to get 8577.5 Earth days. Divide that by 456.25 to get 18.8.

And this seems to be right after all!! Wow, thank you so much, Colibri and chrisk!

This absolutely helps, chrisk! I was about to ask for a consistent formula to use moving forward. That’s exactly what I was looking for. Yay!

I can’t believe how much obsession I have for details that literally no one else in this game is likely to care about. I worry myself sometimes.

Well, more than just sometimes.

Thanks again, guys!

Age doesn’t matter to the Brothgarians and they are all hermaphrodites, except for the eunicks, who are only female. But this is largely unimportant as most of them are either convicts or prostitutes.