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The figure for the number of days in a year is an intriguing one. The integer portion will proceed to define the usual length of a Martian year as 668 or 669 days. The fraction, however, is not as obliging as the corresponding value of 0.2422 for Earth, and will lead us down some interesting new calendric paths. |
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You may now proceed to determine two more parts of the Martian calendar: |
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The division of 668 days into months. |
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The devising of a leap year rule from the fraction, 0.5994731. |
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9.13.2.1.4
Months in the Year |
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At this point, you are not entirely constrained by astronomy but need to begin considering other factors. |
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Considering the division of the Martian year into months, you are free to concentrate on months in the sense of solar months, arbitrary subdivisions of the solar year, untied to lunar motion, for the simple reason that Mars has not one, but two, moons, and both are completely unsuitable for defining a month. Both are tiny and nearly invisible from Mars. Both rotate extremely quickly Phobos in 7 hours 39 minutes and Deimos in 30 hours 18 minutes. Using Phobos to define a lunar month would produce a Martian month of about 11 hours less than half a day. Neither moon can be seen in the higher latitudes, and both spend long periods eclipsed by the shadow of Mars. Martian months, then, will have nothing to do with Martian moons. At this point, you need to begin considering several facts. First, factor the value of the length of the year, since you are compelled to deal with this number. Observe that 668 = 22167. That is, the year divides neatly into quarters, which is a serendipitous result, since Mars has observable seasons. You will want the calendar to reflect seasons. |
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The number 167 is prime, so something must be done with it. If you attempt to maintain a 12-month year to reduce the psychological impact of the Martian calendar, observe that a quarter must consist of 167 days, and each month must contain 167/3 = 55.6666 days. This result immediately suggests a pattern of (55 + 56 + 56 = 167) days in each quarter. Other options are possible. A 16-month year would have (41 + 42 + 42 + 42) = 167 days in a similar pattern. |
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Choose a 12-month year. The only reason for this choice is to make the Martian calendar more congruent with common Terran calendars and less psychologically stressing for early users. |
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9.13.2.1.5
Leap Year on Mars |
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Determining a leap year rule from the fraction is also partially constrained by the mathematics and partly a matter of choosing among several alternatives. First, observe that 0.5994731 is larger than 1/2, so that 0.59947312 = 1.1989462. Thus, you accumulate an extra day every two years, and the leap year rule must take account of this situation by declaring a leap year quite often. Your first effort is to find a simple ratio that approximates the fraction 0.5994731. |
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