I’m writing some decently-hard science fiction which revolves heavily around an alien species on another planet, far away from our Solar System. Rather than live on a rocky planet, this species originates on the moon of a gas giant, superficially similar to Titan. All that worldbuilding has been done: their schooling systems and societies and economy are largely similar to that of Earth’s.

The thing is, the years are longer on this planet. The orbital period of the home planet of this species is about 5.7 Earth years, and that’s how they measure time. “Conveniently”, they use time units so that they have 12-hour days and 8-day weeks and 500-week years, but that means when they say “year”, they mean about 5.7 Earth years.

That’s all well and good but the story is written from the perspective of one member of this alien species who’s three years old (equivalent to about 17 Earth years; she’s finishing high school) before first contact is made with humanity. I anticipate most of my readers will be humans and what I’m uncertain about is how to establish to the reader that the years here are different than on Earth. I feel really weird saying “… which is equivalent to x Earth years” because Earth and humans aren’t referenced until much later in the story.

Is there a convenient solution to problems of this variety?

  • 4
    "I anticipate most of my readers will be humans [...]" No, never anticipate that. It's more likely that everyone who reads your group is an intelligent space amoeba screaming frantically while holding on to the remainders of Pluto's formerly invisible 32953'th moon. Why? Simple. Who wouldn't want to have their work read by amoebas instead of by intelligent human beans? No criticism that way.
    – Daemons
    Commented May 31 at 0:44
  • 2
    @Daemons Realistically, most of the readers will be webcrawlers to feed algorithms (such as search engines and AI).
    – Ben
    Commented May 31 at 11:03
  • 2
    Is your "year" one orbit of the planet about the sun, or one orbit of their home moon about the gas giant? I would think that both time spans would have significance in this culture. Even on earth we have months based on the orbit of our moon.
    – David K
    Commented May 31 at 11:41
  • 1
    Good clarification - their moon orbits their planet in 8 days, which they call 1 week, and the planet orbits around the Sun every ~500 weeks, or ~4000 days @DavidK. Commented May 31 at 12:22

5 Answers 5


Just don't call them "years", call them an "orbit". Presume they are past their local Copernicus; they know their world orbits a sun (or planet).

"I am three orbits old; that means I am officially an adult and no longer my parent's responsibility, I can vote, I can get married, I can drive on my own, I can go to college."

Of course you should do that in a scene. But just get used to making it a part of the language, they measure long time in "orbits", and perhaps shorter time in Seasons (if the orbit is not circular, like ours is not circular) or "quarters", a quarter of an orbit, or "quints", a fifth of an orbit.

Do not try to "borrow" English terms for their measurement of time, or distance. Even on Earth, not everybody always used the same terminology for these. Such measures are idiosyncratic; our word "mile" comes from the Roman "milia passum" which was "one thousand paces", each pace was five "feet", but the measure of a "foot" was different for Romans, so their 5000 feet was our 5280 feet.

All of this would have no meaning to aliens, they will have their own idiosyncratic measures for distance, weight and liquids, and they will have their own idiosyncratic measures for time as well.

Your story will not seem realistic if you just borrow English words for all of this. Make up your own history of how their measurement system originated, and use your own words.

Readers will get used to them. Due to tracking child development, if it occurs roughly on the same schedule as humans, you are going to need subdivisions of the "orbit". You cannot put first graders and sixth graders in the same classroom, they are going to need subdivisions of the orbit that approximate an Earth year, and probably Earth Seasons within that. Perhaps weeks as well (and "7 days" is also an entirely arbitrary number of days in a week, roughly based on quarter Moon phases, which aliens might not have.)

Edit: Jack Aidley in the comments claims "Invented units are a bad idea. "It was four k'aih to their camp" communicates nothing and a text with many invented words rapidly becomes irritating to the reader.

There is an element of truth in this. First, do not make your invented units difficult for a reader to pronounce and remember. Second, always invent a way to introduce your measurement systems in context, and in isolation, meaning don't use your time measure to explain your distance measure, like "a kilometer is a 12 minute walk," or "a mile is a 20 minute walk," unless the reader has a good grasp on your time measure.

Keep in mind the real-life disparity between "Fahrenheit" and "Centigrade", or "Kilometers" and "Miles", "meters" and "yards", "liters and gallons", "kilograms and pounds".

To an extent, this is all about context. In centigrade, 10C is chilly, you need a coat or at least a sweater (50F).

As a writer, ultimately, the measures only matter in how they affect your characters, physically or time-wise, and that is how you introduce them. What does a baby weigh? How far is it to school, and how much time does it take to walk there? How long is it between meals? How long do you normally sleep? Implicitly explain your measures by "show, don't tell." Use them in relatable circumstances within scenes.

  • 2
    I think that’s reasonable. I have a conlang and alphabet set up for them already, but obviously I’m not going to type strange glyphs of an alien language into my book and expect people to read it. I should get a system of measurement set up for them, too. Thank you! Commented May 30 at 15:53
  • 4
    Invented units are a bad idea. "It was four k'aih to their camp" communicates nothing and a text with many invented words rapidly becomes irritating to the reader. The Aliens aren't speaking English either, so just treat it as translated into our units for convenience. Commented May 31 at 6:27
  • 3
    '(if the orbit is not circular, like ours is not circular)' classic nitpick, but it has to be done. Our orbit is only a little off circular, and the different distances to the sun makes little difference - in fact we are closest to the sun in January I believe! It is instead the tilt of the earth's axis that makes the seasons. Which is also why they're different in the north vs the south.
    – Muzer
    Commented May 31 at 15:28
  • 1
    I feel like Farscape did a reasonably good job of using weird units and not making it a big problem. I may not know what an arn or microt are, but context gives the idea that the former is a span on the order of an hour or two, while the latter is probably just a second or two. "If you do not surrender in five microts, I'll blow you out of the sky! five... four... three..." vs "My suit is running low on oxygen---I've got maybe two arns left." Similarly, your idea of tying developmental milestones to time makes good sense. (+1) Commented Jun 1 at 16:26
  • 1
    @XanderHenderson Exactly. Invent situations where the meaning is implied. It doesn't matter if a microt is 1 or 2 seconds, intuitively we know "micro" means small, and "arns" sound close enough to "hours" to guess what it means. And we can create drama without knowing the exact meaning: "I've got maybe two arns of oxygen left." response: "The ship is at least two and a half arns from here!" It doesn't matter exactly( how long an arn is; we have a problem! Introduce measures with *magnitude implied; and if possible such that "good" and "bad" is relative so a precise definition is not needed.
    – Amadeus
    Commented Jun 1 at 21:35

The notion that all novels must be written in a limited first person viewpoint is an absurd misconception strangely prevalent among beginning writers today. Maybe this stems from growing up with the recent fad in YA fiction to write everything in this viewpoint. In adult fiction, a third person viewpoint is much more prevalent, even today, because it is much more flexible and adaptable.

Especially when the reader is taken to an unfamiliar world, a viewpoint that shifts between limited third person and omniscient worldbuilding is quite common. Think of The Lord of the Rings, which sticks closely to the current experiences of each of its viewpoint characters, without giving anything away that the protagonist doesn't know, but easily provides all the background knowledge the reader needs alongside this close personal experience.

I think it will take nothing away from your story, if you tell it from a similar "limited omniscient" viewpoint.

If you want to write from a limited first person viewpoint, it is important to understand what the word year signifies. It is both a standardized unit of measurement (356 Earth days long) and a label for a very complex concept that includes knowledge about the seasons on Earth, the public holidays of your culture, the semesters of school and university, the fact that work is structured in seven day weeks, and other elements of the temporal social rhythm of our societies.

When you say that a person (on Earth) is three years old, all of that is activated in your mind. The word year doesn't just mean "three birthdays", it implies all of what I described above and more. And when you write that your character is three years old, that is what is activated in the mind of the reader, as well.

That is, when you use the term year, you aren't actually writing from the first person perspective of your alien viewpoint character at all! You are mixing Earth concepts into the alien world, much as if you said they were drinking coffee or watching soccer. They don't! Because they don't have coffee and soccer. And they don't have a year.

If you translate a story from, say, British English with its imperial measurements, into a language with a metric system and for readers who are unfamiliar with feet and miles, you won't translate "John drove at 50 miles per hour" into "[John drove at 80 miles per hour]." (For your convenience I represent the foreign language as English in square brackets.) You will convert the units of measurement as well and write "[John drove at 80 kilometers per hour]." You need to do the same with the Earth year.

The options you have are:

  • Invent an alien term: "Xyl was three neamei old." (Italicize foreign words.)
  • Translate that term into scientific terms: "Xyl was three seasonal cycles/orbits/... old." (Similarly, an alien "day" could be called a planetary rotation.)

Both options require that the readers endure not understanding everything immediatley. This can become quite strenuous and irritating for some readers if you introduce too many alien concepts before you explain them. Some people like that, and some people don't. If you write science fiction or fantasy, many of your readers will likely have an open mind for such an approach.

The third option, besides writing in a "limited omniscient" viewpoint and immersing your readers in a truly alien viewpoint, is to provide unobtrusive explanations as you go along. I assume that in a hard science fiction novel you have a good reason why you create a world with such a different orbital length, and I'm sure you have carefully constructed all the consequences it will have for the life on that planet and the culture for that intelligent alien species. For example, if you let the reader know how the life cycle of the aliens relates to their own planetary year, the more clever readers will likely understand that the alien year doesn't correspond to the Earth year. They won't be able to deduce the exact length of the alien year from the alien perspective alone (because if the aliens are unaware of the Earth year there will be nothing in their culture that corresponds to it), but the readers will be alerted to the difference and they may understand that it is significantly longer than our years are.

  • 1
    Your "seasonal cycles" reminds me: there's a common practice in fantasy of evoking old-timeyness by referring to years as "winters"; "I was just thirteen winters old when..." "The town's been here for well over a hundred winters...". (I assume winter is chosen because it's arguably the most distinct season, even for people with no knowledge of agriculture.) This may have been actually common in English at some point, I'm not sure, and it certainly sounds somewhat archaic and poetic now, but it would be a valid option regardless of the planet, as long as the planet has noticeable seasons.
    – Hearth
    Commented May 31 at 17:23

The most convenient way to get this across to the reader is for the narrator to just relate their experiences in their own frame of reference.

For instance:

"I graduated high school when I was three years and one month old. It had taken me a whole year — which was four months faster than my friends."

Shows the reader that years might be different in this story. That one sentence leaves the door open to two reasonable interpretation — the narrator is some sort of child prodigy or years are longer. If the narrator related how long her parents had been married — five whole years — or that they were going to grandma's 15th birthday party, then you minimize the chances of the erroneous interpretation.

Alternatively, if the opening chapters are epistolary — her diary (translated into English by after contact with humans) — then you can use footnotes.

How precisely you communicate these details depends on how important they are to the story. To me, I think the important fact is that years are longer here, and the fact that its 5.7 of our years to one of their years isn't that important. I'm sure somewhere in your story it will make sense for the narrator to learn that a terran year is 0.175 of her own year.


Have a human character work out their earth year age(s) when we first meet the alien character(s) and then leave it alone, harping on about the age of a character when it isn't a point of the plot tends to be tedious. If you need to convey time within the narrative have the character pause and work it out in earth units for her human friends "that was, I think you would say [insert number here] minutes/hours/days/weeks/months/years ago", where appropriate and use purely alien units that the reader can try to work out, or not, the rest of the time. You can have fun with that when it turns out the alien(s) have their conversion wrong as well.


One thought that comes to mind--perhaps not the best option for explaining but one that allows for additional character building--would be to simply have an encounter between two characters that comes about because of it. A misunderstanding leading to something unexpected is probably the easiest way to do this.

Say for instance that an earth person says that they're thirty years old, and an alien person comes to see this amazingly long-lived and undoubtably very wise elder, only to find someone about their own age. Perhaps an alien puts out an ad for a caretaker for their 12-year-old relative and a human shows up expecting to be babysitting a preteen and instead ends up assisting an elderly widower.

This gives you a chance to explain things, and also a chance to show how your characters act under unexpected circumstances (always good for characterization), but it can easily feel a little forced.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.