# Thread: A calendar for Titan

1. ## A calendar for Titan

I don't math good. I've been trying to come up with a calendar for a colony on Titan. I assume that any colonists would employ three calendars: a native calendar set to the rhythms of their own world; a common, utilitarian calendar used for communication between worlds, and the native Earth calendar. The common calendar would be a simple count of 360 24-hour days, with no regard for months or weeks.

This native calendar, the "long calendar", would be of very little practical use, mainly used for timing native seasonal celerations, such as the coming of the winter rains, and the Great White Spot.

The Saturnian year consists of 674.770774537 Titanian days. What is the pattern of leap days required to keep pace with the seasons, assuming a 675-day calendar?

2. Are you talking about a human colony on Titan or native Titans? I don't know why humans living on Titan would have "native seasonal celebrations"; its not like they are going to go outside without a spacesuit to enjoy the winter rains. Why would they use anything other than an Earth calendar? Why would they get rid of months and weeks; its not like months and weeks are tied to any particular Earth events?

3. Are you talking about a human colony on Titan or native Titans?
Human colonists

I don't know why humans living on Titan would have "native seasonal celebrations"
Because they're proud of their home.

its not like they are going to go outside without a spacesuit to enjoy the winter rains
Why not? How is that different from going out in the rain with an umbrella?

Why would they use anything other than an Earth calendar?
Because the Earth calendar is tied to the moon and the seasons, neither of which apply to Titan. Every other world would use a calendar tied to them; Martian colonists would use a calendar tied to their own seasons, Ceresians theirs and so on.

Why would they get rid of months and weeks; its not like months and weeks are tied to any particular Earth events?
But they are. Earth's months are tied to seasons. What's the point of using terms like "August" or "May" when the connotations of those months are moot? Also, someone on Titan during winter may want to contact someone on Mars during summer. Each would have to use the same dating system, so it makes sense that it's as simple as possible.

4. Originally Posted by parallaxicality
I don't math good. I've been trying to come up with a calendar for a colony on Titan. I assume that any colonists would employ three calendars: a native calendar set to the rhythms of their own world; a common, utilitarian calendar used for communication between worlds, and the native Earth calendar. The common calendar would be a simple count of 360 24-hour days, with no regard for months or weeks.

This native calendar, the "long calendar", would be of very little practical use, mainly used for timing native seasonal celerations, such as the coming of the winter rains, and the Great White Spot.
I don't see any utility to that common calendar myself. What good does it do?
The Saturnian year consists of 674.770774537 Titanian days. What is the pattern of leap days required to keep pace with the seasons, assuming a 675-day calendar?
According to [1], the Saturn sidereal year is 10759.22 days (weirdly, it says the Saturn *tropical* year is over 12 days shorter), and according to [2], Titan's rotation period (equal to its orbit around Saturn) is 15.945 days.

10759.22 / 15.945 is 674.77077453747, as you have there. But just as Earth's day is longer than its rotation period, Titan's day (sun up to sun up) would be 15.968665 days, which is 10759.22/(10759.22/15.945 - 1).

There would be one less "Titan Day" in the year. So, assuming a 674-day calendar, you'd have .229225463 extra each "year". After four such years, you'd have an extra day that you would have to drop. Doing that means you'd drop 4-4x.229225463 too much every four years, and you'd want to skip the drop every 4x12 years, but leave it every 4x12x354 years ... or so. 0.7707745*4*12*354=13,097.0009 days, and 4*12*354-12*354+354-1=13,097

[1] https://nssdc.gsfc.nasa.gov/planetar...aturnfact.html
[2] https://en.wikipedia.org/wiki/Titan_(moon)

5. Thanks. Wow that's an accurate calendar. As to the utility of the common calendar, what use would people living off Earth have for Earth's leap days, or 5 extra days a year? Those are only useful to people living on Earth, and forcing the rest of the Solar System to use a cumbersome calendar that does not reflect their own lives would be seen as cultural imperialism. I can see older people pining for the "old country" using the old calendar to track holidays like Christmas, but why would people born and raised on Mars or Ganymede care about that?
Last edited by parallaxicality; 2019-Apr-15 at 11:59 PM.

6. Originally Posted by parallaxicality
But they are. Earth's months are tied to seasons. What's the point of using terms like "August" or "May" when the connotations of those months are moot?
They are not necessarily tied to seasons. From a European perspective, sure. But they use the same calendar in the Southern Hemisphere, without changing the season names to fit their seasons, and in equatorial reasons, where there are often just dry and rainy seasons.

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7. Regarding the question, I think you would definitely want to keep the same seconds and minutes as on earth, because machines and instruments are made that way. And you would definitely want to keep the same days because our circadian rhythm is tied to it and we cant function in 16-day cycles.

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8. Originally Posted by Jens
They are not necessarily tied to seasons. From a European perspective, sure. But they use the same calendar in the Southern Hemisphere, without changing the season names to fit their seasons, and in equatorial reasons, where there are often just dry and rainy seasons.

Regarding the question, I think you would definitely want to keep the same seconds and minutes as on earth, because machines and instruments are made that way. And you would definitely want to keep the same days because our circadian rhythm is tied to it and we can’t function in 16-day cycles.

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True but they are still tied to the same cycles of the same planet. Southern hemisphere dwellers have connotations about March and July just as northern hemisphere dwellers do, just different ones. But how does that work when your world follows a completely different seasonal cycle?

I hadn't thought about minutes and seconds. I was going to decimalise time ala the Revolutionary Calendar but you're right. The QWERTY effect rules all.

9. Also, about the seasons, I would think that as long as you are a basically artificial habitat, it wouldn't make any difference, so there would not be any reason to adopt a new calendar. You would surely want to keep track of where Titan is compared to Saturn, because this would be important for things like communication with earth and travel, but there wouldn't really be any reason to adopt it in daily living. Of course, if you could somehow terraform Titan and really make it have seasons, then sure, you would probably want to adopt some local system.

10. Originally Posted by parallaxicality
Thanks. Wow that's an accurate calendar. As to the utility of the common calendar, what use would people living off Earth have for Earth's leap days, or 5 extra days a year? Those are only useful to people living on Earth, and forcing the rest of the Solar System to use a cumbersome calendar that does not reflect their own lives would be seen as cultural imperialism. I can see older people pining for the "old country" using the old calendar to track holidays like Christmas, but why would people born and raised on Mars or Ganymede care about that?
Well, your op assumes they would use three calendars, one of which is ours, for obvious reasons. I cannot figure out a reason for using just 360 days--wouldn't that just complicate shifting back to the first calendar, when necessary?

I dunno why we'd have to decimalize time. We tried it once, and even the metric world abandoned it. Base 60 is still one of the most commonly used bases in the world.

11. Why would it ever be necessary? The old Earth calendar would be mainly for keeping holidays like Christmas. It would have the same import as the Jewish or Chinese calendars do in the US. For interplanetary commerce, all you need is a day count.
Last edited by parallaxicality; 2019-Apr-16 at 01:32 AM.

12. Originally Posted by parallaxicality
Why would it ever be necessary? The old Earth calendar would be mainly for keeping holidays like Christmas.
Personally I would think that as long as the vast majority of humans are living on earth, the easiest thing for a colony would simply be to use that one.

13. Originally Posted by parallaxicality
Why would it ever be necessary? The old Earth calendar would be mainly for keeping holidays like Christmas. It would have the same
import as the Jewish or Chinese calendars do in the US. For interplanetary commerce, all you need is a day count.
Well, there you go, the Julian Date

https://aa.usno.navy.mil/data/docs/JulianDate.php

Originally Posted by parallaxicality
I don't math good. I've been trying to come up with a calendar for a colony on Titan. I assume that any colonists would employ three calendars: a native calendar set to the rhythms of their own world; a common, utilitarian calendar used for communication between worlds, and the native Earth calendar. The common calendar would be a simple count of 360 24-hour days, with no regard for months or weeks.
No need for years either!

14. Originally Posted by grapes
According to [1], the Saturn sidereal year is 10759.22 days (weirdly, it says the Saturn *tropical* year is over 12 days shorter)

::snip::

[1] https://nssdc.gsfc.nasa.gov/planetar...aturnfact.html
I've now found a reference where the Saturn's tropical year is 21 *hours* shorter, instead of 12 days. The earth's tropical year is just 20 minutes shorter than its sidereal year. (google books, Saturn and Its System, Richard Anthony Proctor, p164)

15. Here's a proposal for Mars, based on what has already been established. It looks simple! [cough]

https://www.sciencedirect.com/scienc...926?via%3Dihub

My brain hurts.

16. And let's be honest, landing a human colony on Titan and keeping it alive is going to be, um, super-hyper-difficult. We'll do it eventually, unless the Titanians tell us not to bother.

But we can go to Callisto. A proposal was worked out for it in 2003 by NASA.

https://web.archive.org/web/20120119...ant/bethke.pdf

This would make a very interesting calendar. Likely the explorers & colonists would just use Earth time at first, but we have a calendar for Mars and no one's been there yet. Why bother with a calendar?

Because active robots are there. Once you put an active robot down on any world, the impulse for humans back on Earth is to make a calendar for that world. If we'd been able to keep a robot "alive" on Venus for longer than half an hour, we'd have a Venusian calendar by now.

So, a Titan calendar makes a lot of sense for the robotic submarines NASA's been thinking of landing in the seas there. I support a Titan calendar.

So, then... Callisto. Robots will be everywhere there, safely out of the Jovian radiation field that would degrade their parts. Calendar, anyone, for the robot army to come?
Last edited by Roger E. Moore; 2019-Apr-16 at 06:21 PM.

17. Originally Posted by parallaxicality
The Saturnian year consists of 674.770774537 Titanian days. What is the pattern of leap days required to keep pace with the seasons, assuming a 675-day calendar?
Would it be helpful to skip the leap year concept altogether and divide up the 0.770774537 Titanian day throughout the other 674 days? Humans might not mind since the local cycles are going to be so far out of sync with their internal biorhythms. They turn on lights inside their colony homes for work, turn the lights off when sleeping. So a Titan year consists of 674 Titan "days", which are each 1.00114358239911 actual Titan days long.

LATE NOTE: If this idea doesn't work, it's okay to tell me so.

LATER NOTE: Forget it, this was a dumb idea. Sorry!
Last edited by Roger E. Moore; 2019-Apr-16 at 08:20 PM.

18. Wait a minute, something occurred to me. Would it not be more, um, locally relevant for colonists on the moon of a given planet to know the length of a synodic day, i.e., the length of a "day" from sunrise to sunrise, or sun at zenith to sun at zenith?

In the case of captured-rotation giant moons, the synodic day (or whatever time unit you are using) would be based on solar and planetary alignment, such that the satellite falls on an exact line from Sun to home planet. If you use a "midnight to midnight" system, it would be Sun-Saturn-Titan, which would be Titan's "midnight" (particularly if eclipsed--and an eclipse would be important). If a "noon to noon" system is used, it would be Titan exactly between the Sun and Saturn when seen from above, 90 degrees upward from the orbital plane of Saturn.

The problem is, I cannot find the synodic period lists for any major satellite in the Solar System. Is there a place where this is gathered together in a table or something? The listed tables seem to be for sidereal days, based against the distant stars.

LATE ADD: Found a formula for it, will try it later.

https://www.1728.org/synodic.htm
Last edited by Roger E. Moore; 2019-Apr-16 at 08:25 PM. Reason: found formula

19. A few reasons why, for active robots or live humans inhabiting a natural satellite of any planet, or inhabiting an airless planet, a synodic calendar based on local bodies would be preferable to any other.

1. Solar power. For Mercury and the Moon, solar power would be significant. Mercury rotates, and the Moon has captured rotation around the Earth. The placement of solar power stations for robots or humans becomes critically important. If volatile gases or water are brought to the Moon, you could get solar-heated steam turbines. The position of the Sun is all important. Any sort of thermal power from the sun, same thing.

2. Atmospheric effects caused by sunlight. On Titan, there might be storms, winds, actual weather affected by the distant Sun. It might be important for colonists & robots to work around this.

3. Natural lighting to see by. 'Nuff said.

4. Eclipses by the primary planet. These will interrupt solar and thermal power.

5. Observation stations looking at primary planet. Phases and other cycles will follow a synodic period exactly.

20. Originally Posted by Roger E. Moore
Wait a minute, something occurred to me. Would it not be more, um, locally relevant for colonists on the moon of a given planet to know the length of a synodic day, i.e., the length of a "day" from sunrise to sunrise, or sun at zenith to sun at zenith?
That's what I've been discussing!
Originally Posted by grapes
10759.22 / 15.945 is 674.77077453747, as you have there. But just as Earth's day is longer than its rotation period, Titan's day (sun up to sun up) would be 15.968665 days, which is 10759.22/(10759.22/15.945 - 1).

21. Originally Posted by grapes
That's what I've been discussing!
Well... I'm slow. Okay, maybe slow is not the right word.
Last edited by Roger E. Moore; 2019-Apr-17 at 12:01 PM.

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