Suggested by M. Vertregt and recounted by Francis Graham
Our Earthly calendar is tied to the motions of the Earth with respect to the Sun. 1 year is 365 1/4 days, the time it takes for Earth to orbit the Sun. 1 day is the average time from midnight to midnight, the time for a point on the opposite side of the Earth to directly face the Sun.
However other planets have different motion relations with the Sun. Of particular interest is Mars. Are we to label our days on Mars by Earth's motions? Or are we to make Mars' motions the basis of time on that orb?
Initially, one might expect the early astronauts to use GMT. However, at some point, the inhabitants of Martian bases will look at their reflections, and say, in a Bradburian way, "We are the Martians!" and reckon time Mars style.
The Martian sidereal day is 40 minutes longer than the Earth sidereal day of 23h 56 m 4 s., to be precise, 24 h 39 m 35 s = 88,775 sec. An initial simple way of coordinating Mars and Earth time is to set Earth clocks back 2 hours every three days.
We might also experiment with decimalized time units. Each Mars day has 10 Mars hours, say. Each Mars hour has 100 Mars minutes. Each Mars minute has 100 Mars seconds. We would probably not want to call them seconds so as to not confuse things with Earth seconds, since the Earth second has become the standard S.I. physical unit. The Mars seconds could be called "clicks". The Mars minute could be called a "pause" and each Mars hour a "temp". The Martian day already has a name thanks to the Sojourner people. It's called a "sol".
Our Earth week marks the rough time between phases of the Earth's Moon. Since Mars' moons Phobos and Deimos produce no dramatic phenomena, we can arbitrarily set a Martian week. How about ten days?: Sunday, Mercday, Venuday, Earthday, Marsday, Joviday, Saturday, Uraniday, Neptuday, Plutoday? Seems logical to me. One less big body in the dynamical system allows such arbitrary assignations.
Mars' year is 686 Earth days 23h 30 m 41 s = 59355041 sec. This is 66,860,086 clicks or 668.6 sols, which is as poorly divisible as 365, factors being 4 and 167. But if we have 670 sols per Martian year and 660 sols in a "short year" every 7 Mars years, we have the added advantage of having the same Mars weekday on the same date in a Mars year. This is something Achelis tried to do with the Earth calendar after World War II, with the so-called "World Calendar", and almost succeeded, but failed ultimately. So we can do it fresh on Mars.
50 Mars years, a pentakonade, counts 33,430 days, 7 septades of 7 Mars years each followed by one year. Each 7th year in a septade is a short year of 660 days followed by regular 670 day years.
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