Last year by far the best movie I saw at the cinema was "The Martian", known in China as "Mars Rescue" and shown a few months after its release in the US. After looking around at some calendaring systems for Mars, I found none of them suitable so I invented one myself.
The concepts of "Martian day" and "Martian year" are quite intuitive, and form the basis of this calendar.
The system used by US robotic missions to Mars of making the Martian second 2.75% longer than the Earth second is a good system, so there's 60 Martian seconds in a Martian minute, 60 of those in a Martian hour, and 24 of those in a Martian day, called a "sol". The Martian time zone used by US missions is whatever puts the Sun directly overhead at Martian noon, but perhaps later on Mars should be divided into 24 time zones.
The 7-day week has been around for at least 2,500 years, and is now standardized by virtually every society on Earth. A 7-sol week would also be a natural choice for Mars, but there's one additional feature of a Martian week which would make it special, and forms the basis for the subsequent decisions in designing this calendaring system: The day of the week on Mars should be the same as the current day of week on Earth.
Because 1 Martian "sol" is the same as 1 day and 40 minutes on Earth, matching the Martian day of week to the Earth one will cause a 1-sol slip around every 37 sols, so a day of week will need to be skipped to reset the Martian day of week back to the Earth one. A second design decision is that the same day of week should be skipped each time. Because the present international standard is that Monday is the first day of the week and Sunday the seventh, perhaps it's best that the last day of the week, Sunday, be skipped. This would happen once every 5 or 6 weeks.
There should be a time period roughly matching what's known as a month on Earth. The third design decision is that a Martian month would end whenever a Sunday is skipped. So a Martian month would always be 34 or 41 days long. On average, every third month would be 41 days long, and the other two 34 days long. Because a Martian year is about 668 sols long, this puts the number of Martian months per Martian year as usually 18 and sometimes 19.
The timing and name of a Martian month could roughly follow those on Earth, or they could follow the seasons on Mars, or perhaps a bit of both. We've tried to do both in our fourth design decision: every second Martian month name will match the current month on Earth, and every other Martian month will match the seasons on Mars. Tentatively, we've used the English month names January to December for the Earth months, and the Horoscope signs Aries to Pisces for the seasons on Mars. The same Earth month name won't be used twice only one Earth year apart but forward to the following Earth month if necessary. Therefore, all month names in a single Martian year will be unique.
I've written a quick script in Golang to look at the distribution of month names using these rules over 25 Martian years. Aries marks the beginning of Northern Spring, and the distorted season lengths on Mars are accounted for...
Jan:22, Feb:16, Mar:16, Apr:19, May:20, Jun:21, Jul:19, Aug:19, Sep:20, Oct:18, Nov:18, Dec:22,
Ari:21, Tau:21, Gem:23, Can:20, Leo:21, Vir:17, Lib:15, Sco:18, Sag:15, Cap:16, Aqu:21, Pis:22,
The least frequent seasonal month names are Libra and Saggitarius, which matches winter and autumn being the shortest months on Mars. February, the shortest month on Earth, is also among the least frequent Earth-month-named months on Mars.
The full data, where a + after the month name denotes a 41-day month...
月: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
1年: Jan+ Ari Mar+ Tau Jun Gem+ Aug Can Nov+ Leo Feb Lib+ Apr Sco Jul+ Cap Sep Aqu+ Dec
2年: Pis Jan+ Tau May Gem+ Jun Can Oct+ Leo Nov Lib+ Feb Sco Apr+ Cap Jul Aqu+ Sep
3年: Pis Dec+ Ari Mar Gem+ May Can Aug+ Leo Oct Vir+ Jan Sco Feb+ Sag Jun Aqu+ Jul Pis+
4年: Nov Ari Dec+ Tau Mar Gem+ May Leo Aug+ Vir Oct Sco+ Jan Sag Apr+ Aqu Jun Pis+
5年: Sep Ari Nov+ Tau Dec Gem+ Mar Can Jul+ Vir Aug Lib+ Oct Sag Jan+ Cap Apr Pis+
6年: Jun Ari Sep+ Tau Nov Gem+ Feb Can May+ Leo Jul Lib+ Oct Sco Dec+ Cap Jan Aqu+ Apr
7年: Ari+ Jun Tau Sep+ Gem Nov Can+ Feb Leo May+ Lib Jul Sco+ Oct Cap Dec+ Aqu Mar
8年: Pis+ Jun Ari Aug+ Gem Sep Can+ Jan Leo Feb+ Vir May Sco+ Jul Sag Oct+ Aqu Dec Pis+
9年: Mar Ari Jun+ Tau Aug Can+ Nov Leo Jan+ Vir Apr Sco+ May Sag Sep+ Aqu Oct Pis+
10年: Dec Ari+ Mar Tau Jun+ Gem Aug Leo+ Nov Vir Jan+ Lib Apr Sag+ Jul Cap Sep+ Pis
11年: Dec Ari+ Feb Tau May+ Gem Jun Can+ Oct Vir Nov+ Lib Jan Sag+ Apr Cap Jul+ Aqu Sep
12年: Ari+ Dec Tau Feb+ Gem May Can+ Aug Leo Oct+ Lib Jan Sco+ Mar Cap Jun+ Aqu Jul
13年: Pis+ Sep Tau+ Dec Gem Apr+ Can May Leo+ Aug Vir Oct+ Sco Jan Cap+ Mar Aqu Jun+
14年: Pis Jul Ari+ Nov Tau Dec+ Can Apr Leo+ May Vir Aug+ Sco Oct Sag+ Jan Aqu Mar+ Pis
15年: Jun Ari+ Sep Tau Nov+ Gem Feb Leo+ Apr Vir Jul+ Lib Aug Sag+ Dec Cap Jan+ Pis
16年: May Ari+ Jun Tau+ Sep Gem Nov+ Can Feb Vir+ Apr Lib Jul+ Sag Oct Cap+ Dec Aqu Mar+
17年: Ari May Tau+ Aug Gem Sep+ Can Jan Leo+ Feb Lib Jun+ Sco Jul Cap+ Oct Aqu Dec+
18年: Pis Mar Tau+ May Gem Aug+ Can Nov Leo+ Jan Vir Apr+ Sco Jun Cap+ Sep Aqu Oct+
19年: Pis Dec Ari+ Mar Gem+ May Can Aug+ Leo Nov Vir+ Jan Sco Apr+ Sag Jun Aqu+ Sep Pis
20年: Dec+ Ari Feb Tau+ May Gem Jul+ Leo Aug Vir+ Nov Lib Jan+ Sag Apr Aqu+ Jun Pis
21年: Sep+ Ari Dec Tau+ Feb Gem May+ Can Jul Vir+ Oct Lib Jan+ Sag Mar Cap+ Apr Pis
22年: Aug+ Ari Sep Tau+ Dec Gem+ Feb Can May+ Leo Jul Lib+ Oct Sco Jan+ Cap Mar Aqu+ Jun
23年: Pis Aug+ Tau Nov Gem+ Dec Can Apr+ Leo May Lib+ Sep Sco Oct+ Cap Jan Aqu+ Mar
24年: Pis Jun+ Ari Aug Gem+ Nov Can Feb+ Leo Apr Vir+ Jul Sco Sep+ Sag Dec Aqu+ Jan Pis
25年: May+ Ari Jun Tau+ Aug Gem+ Nov Leo Feb+ Vir Apr Sco+ Jul Sag Sep+ Aqu Dec Pis+
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The day of the week on Mars should be the same as the current day of week on Earth
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The same day of week should be skipped each time
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A Martian month would end whenever a Sunday is skipped
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Every second Martian month name will match the current month on Earth, and every other Martian month will match the seasons on Mars
Of course there's many more rules we could add to fine-tune the idea. When the Earth is closest to Mars, we could have two consecutive Earth-month-named Martian months, and when Earth is furthest away, have two consecutive season-named Martian months. But these rules roughly show how the 24 month names would be distributed. And this is assuming there's no flaws in my program.
Copyright © 2016 Gavin "Groovy" Grover
Distributed under the same BSD-style license as Go that can be found in the LICENSE file.