Fun_People Archive
5 Jan
Martian calendar - proposal

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From: Peter Langston <psl>
Date: Mon,  5 Jan 98 14:37:30 -0800
To: Fun_People
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Subject: Martian calendar - proposal

From: Anton Sherwood <DASher@netcom.com>

It would be convenient for human settlers on Mars to divide the Martian year
into 24 months.  But how many days should each month have?  If the year is
divided equally by time, obviously each month has 27 or 28 days (the year
is 668.5994 Martian days).  An alternative is to define a month as 15
degrees of motion around the sun, so that the periods between equinox and
solstice are each exactly six months.

Using Kepler's Second Law, I have computed the following lengths for such
months.  Orbital eccentricity is 0.093 and my year begins at northern spring
equinox, L_s=0 (110 degrees after perihelion).  I've done no error analysis
yet; I would like to know how sensitive these months are to an error in the
last digit of the eccentricity or the phase angle.

month#		days		A		B		C
 0		30.01		30		30		28
 1		31.30		31		31		28
 2		32.37		32		32		28
 3		33.10		33		33		28
 4		33.41		33		33		28
 5		33.25		33		33		28
 6		32.66		33		32		28
 7		31.69		32		31		28
 8		30.46		31		30		28
 9		29.10		29		29		28
10		27.73		28		27		28
11		26.43		26.6		26		28
12		25.28		25		25.6		28
13		24.35		24		25		28
14		23.65		24		24		28
15		23.20		23		24		27
16		23.03		23		24		27
17		23.11		23		24		27
18		23.47		24		24		27.6
19		24.09		24		25		28
20		24.95		25		25		28
21		26.03		26		26		28
22		27.28		27		27		28
23		28.64		29		28		28

I hope I haven't blundered somewhere!

In column A, I've rounded according to the rule of largest remainder:  those
months with a fraction larger than .43 are rounded up, those with a smaller
fraction are rounded down, and month 11 is leap-month, with an extra day in
three years out of five.

In column B, to make the months slightly more equal in length, the longer
months are rounded down, the shorter months rounded up.

In column C, I took B a step further: the shorter months get 27 days, the
longer months 28.

Comments?

I'd like to name each month for the brightest star (within the tropics) to
cross the midnight line in that month; that might be an interesting exercise
for someone with access to an appropriate stellar database.
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