Custom calendar

Back with another question: Do you make your own calendar for your setting? How do readers respond to them if you did?

For my Jupiter moons story I'm thinking of putting in a custom calendar for the people who live on those moons. My primary reason is to avoid having to pick an exact date in our standard for the setting. With a seperate calendar you can show passage of time without refering to actual real years.

My second reason is to give it the setting even more an idea of being seperated from Earth.


Another question is this: I'm planning on explaining how the calendar fits together at the start of the novel. With this I mean a single page explaining the thing before the actual novel starts. I deliberately made an easy calendar to not have people break their neck over the math and stop reading before they actually read the story itself. Is this a good idea or shoud I have someone in the story explain the thing? Or should I just I just refer to the calendar and leave people to interpret it from the context.

For my calendar I have a few changes in mind compared to the official one. For instance a week will have 8 days, each named after the Sun and the planets, and days not 24 hours long.

Time keeping is not essential to the stories I have planned. But I do want to have some type of time keeping that makes sence(*) in the area where they are in case an indication is needed at some point.

(*) I don't think it's logical to have 24 hour days and years of 365 days in a region where those are effectively reduced to just arbitary lengths of time.

I've done the research and noticed that a lot of site mention an interesting little tidbit: If you put people in a cave with no way to see the passage of time by means of sunlight they'll slowly shift to a 25 hour cycle.

Anyway, my calendar has a 20 hour work-sleep cycle. One of the things I want to put in the stories is the fact that people got used to the new calendar. That and their bodies have adjusted to the gravity levels of those moons.

The first story involves a group of them returning to Earth and experiencing difficulties adjusting to Earth days and Earth's gravity.

Anthony Ravenscroft said:

I'm surprised at the number of stories that insist a day has 24 hours, or a seven-day week. The former is post-hoc, the latter artificial.

The hour, minute, & second are arbitrary. The Earth month isn't linked clearly to cycles of Luna.

There's the day (one planetary turn) & the year. Other than that, make it up.

Click to expand...

That last line is exactly what I used. Since they are living on the moons of Jupiter I based the calendar on that planet. With that I bumped into a small problem though, which is the fact that Jupiter does one cycle around its own axle in just under 10 hours, which is way too short to be called a day.

So I am now stuck with the following choices:
1: Take 2 cycles and call that a day.
Pro: I can introduce a system similar to AM and PM as extra detail
Con: 20 hours is still a bit short for a day

2: Take 2.5 cycles and call that a day.
Pro: This would make a day almost 25 hours, which is both closer to 24 hours and works out with the 25 hour 'blind' day cycle research mentioned above
Con: I'm now doing timekeeping with half cycles, which is probably too complicated for the average reader

3: Don't bother with this at all and just put in a few vague references to cycles (like: "It's going to take another 15 cycles to get to that asteroid"), parts of a cycle (for timekeeping in the order of magnitude of a few hours) and maybe an arbitrary number of a Jovian year (which means the number would be very low since a year on Jupiter is almost 12 Earth years) and leave it at that.
Pro: Easiest for the reader
Con: To me it feels like a cop-out, since way too many other sci-fi stories use this 'trick'


I've already decided to not mention hours, minutes and seconds and instead go for 1/10th, 1/100th and 1/1000th part of a cycle instead [which in turn brings me to the added task of finding proper names to reference to those instead of using these types of numbers in the text].

At the moment, given the current reaction here, I'm actually thinking of going for #3 though and see how the fans react to it. Then, if they ask for it a lot, I will add the info as an appendix in the second story.

I know all too well what imporper indications can cause from mess that followed the infamous "It'll run .5 past light speed" quote on Star Wars Episode 4 by Han Solo. The main question being what this .5 thing meant, especially since it should indicate that the Millenium Falcon was fast. They later explained this one by introducing it as a class of hyperdrive. The closer to 0 the faster it was. However, many authors after that still made the mistake of thinking it's the higher the faster (Darth Maul's ship in the Cross-sections book is one of those mistakes, it being a courier vessel with a class 3 drive while class 2 and 2.5 is common amongst a lot of civilian ships that don't really need to be fast).


The same movie also has Han Solo refer to his ship as the only one being able to do the Kessel Run in under a certain amount of parsecs. A parsec, like a lightyear, is a distance and not an amount of time. When they found out they explained it like this: The Kessel Run is a race that goes through a region of black holes. In order to get through in one piece you naturally have to steer clear of those black holes as much as possible. If your ship has a faster engine it can get closer to the black holes without being sucked in and you can take a shorter route. Hence: short path in the Kessel Run equals fast engine.


So I'm very familiar with the pitfalls of chosing the wrong term. And I'd rather avoid doing these types of 'clean-ups' or any other ret-conning.

I was also planned to go for the captain's log routine.

One other problem I'm now bumping into is an indication of how old someone is. A year on Jupiter is about 11.8 Earth years (or so, from memory). This would result in some interesting lines of text like for example: You haven't reached the legal age of 1.6 years old yet to be allowed to drink alcohol.

Though I think I'm going to solve that one by putting in months. Since the difference is almost a factor 12 it would mean that indicating age in months would result in almost exactly the same numbers as in Earth years (provided I go for 12 months in a year).

My setting is pretty close to home. The only change in names I'm planning is with days of the week. I want to switch to using planets (except for Jupiter itself) and the sun for those. This should give me my 8 days per week (since Pluto isn't officially a planet any more).