It is all very well to speak of how many days there are in a Martian year, and how these might be divided into months in a given calendar. That, in itself, does not tell us what Martian day it is today.
The two calendars examined in the previous two sections owe their complexity to an attempt to relate closely to the calendar on Earth. The first of them associates each of its months with an Earth month, to allow people's ages in Earth years to be easily measured, and to allow Earth holidays to be celebrated on Mars. The second attempts to associate every Martian day to a corresponding Earth day (with some Earth days left out) so that the day of the week on Mars can be tied to the day of the week on Earth.
This close relationship between them and the Earth calendar is useful for the purposes of this section. It isn't really possible, without having a pre-existing Martian calendar, to say "when" something happens on Mars. First, we have to say when it happened by Earth time to give it perspective.
Thus, the calendar described in the preceding section, which skips some days of the week, can be matched by a corresponding calendar, still tied to the Martian tropical year, in Earth days, which does not skip any days of the week, and which would begin with eighteen months of 37 Earth days each. This can be made the "glue" which relates Earth dates to Martian dates.
One (very valuable and useful) site on the Martian calendar notes a distinction between a vernal equinox year and the tropical year. The difference in length between those years is a short-term phenomenon that averages out, due to the difference between the anomalistic year and the tropical year. Hence, the average of the vernal equinox year over the long term is the tropical year, and it is that year which I will use as the basis of the length of the Martian year. In addition, as it seems entirely likely, either through modifying the Gregorian calendar so that the year 4000 A. D. will not be a leap year, or by switching to the new Orthodox calendar, the current Gregorian calendar will be placed into greater correspondence with the tropical year on Earth, instead of using the Gregorian year of 365.2425 Earth days as the basis for the length of the Earth month, I will use the Earthly tropical year of 365.242189 days.
Again, on Thomas Gangale's site, a table of dates of Martian vernal equinoxes is provided. For the purposes of the calendar which keeps the Earth solar month by having either 22 or 23 Martian months in a Martian year, if the Earth year starts in January, and the Martian year starts in the first Martian month following the vernal equinox, it follows that a good starting point would be a year where the Martian vernal equinox falls in late December on Earth. In that table, it is shown that on December 28, 1943, the Martian vernal equinox occurred at 3:23 PM Greenwich Mean Time. Of course, if that is chosen as the starting point of the calendar, instead of a year when the equinox occurred precisely at the stroke of midnight on December 31st, and the Martian calendar is designed so that its starting point ends a year which has the vernal equinox at the absolutely latest possible point, then some years will start a month late.
Given how the winter solstice is represented by December 25th, a few days late, and the New Year takes place a year later, perhaps it would be more appropriate, if some imprecision in the relationship of the Martian year to the vernal equinox is desired, so as to have an accessible starting point, to rule that the vernal equinox may occur either in the last few days of the old year, or sometime in the first month of the new. In that case, a 1943 starting point for the epoch, now chosen not as the latest, but as the earliest, point at which a Martian vernal equinox can occur relative to the calendar will work out well. If we wish to go in the opposite direction, a Martian vernal equinox occurs at 5 PM Grenwich Mean Time on January 2nd, 2070 in that table.
The average length of a Martian tropical year in Earth days could be used to choose an earlier starting point; starting from a day during one of history's most destructive wars hardly seems appropriate. Also, in 1895, the Martian vernal equinox fell on February 1st at 9:46 AM Greenwich Mean Time. That would relate to the cycle well in terms of whole months, but then another thought occurs; Earth months are not all equal in length. February, of course, is in a way the worst offender. Clearly, we should perhaps look for a year where the Martian vernal equinox fell close to the end of February, or the beginning of March. Although there doesn't seem to be a good candidate for that, as it happens, the Martian vernal equinox fell on 11:09 PM Greenwich Time of April 1st, 1987. This isn't very long ago, which also makes it a convenient point to start from.
April 1st, 1987 fell on a Wednesday.
Given that a Martian tropical year is 686.97258 Earth days long, then the calendar relating the day of the week on Earth to that on Mars would, on Earth, consist of 687 days almost always, being only 686 days long about once every 36.47 years. Thus, after the first 18 months, each 37 days long, an additional 21 days would remain in almost every year. The additional month would be shortened to 20 (Earth) days, again, only about once every 36.47 (Martian) years.
The corresponding Martian calendar has a first 18 months, each 37 days long, followed by 20 days in two years out of every five, and by 21 days in three years out of every five. Thus, the short year in the terrestrial Martian calendar needs to correspond to one of the years in the Martian calendar where the last month is only 20 days instead of 21. Hence, the period of 36.47 years needs to be achieved by alternating spans of 35 years with spans of 40 years between short years; 1.47 years makes 5 years when multiplied by 3.4, and 35 years multiplied by 3.4 becomes 119 years, one less than a multiple of five, thus we will need a cycle following the pattern
35 35 40 35 35 40 35 35 35 40 35 35 40 35 35 35 40
which will be 620 Martian years long, and which will invariably correspond to 425,923 Earth days.
We can now prepare to construct a perpetual calendar for the Martian calendar described on the previous page. There are seven distinct types of Martian years in that calendar, made out of seven distinct types of month. There are months of 36 days which follow an unbroken sequence of days of the week which start on Sunday, Tuesday, Saturday, and Wednesday. To prevent the loss of any Friday, Saturday, or Sunday, there is also a month that should have started on Monday, but instead starts on Sunday and then proceeds directly to Tuesday, and there is a month that starts on Thursday, and ends on a Friday, with the preceding Thursday being skipped, and a month that starts on Friday, ending with a Friday and a Saturday, with the preceding Thursday being skipped. Let us call these kinds of months SU, TU, SA, WE, MS, TH, and FR. In the seven possible kinds of year, the sequence of these months is given below:
a SU TU TH SA MS WE FR SU TU TH SA MS WE FR SU TU TH SA b MS WE FR SU TU TH SA MS WE FR SU TU TH SA MS WE FR SU c TU TH SA MS WE FR SU TU TH SA MS WE FR SU TU TH SA MS d WE FR SU TU TH SA MS WE FR SU TU TH SA MS WE FR SU TU e TH SA MS WE FR SU TU TH SA MS WE FR SU TU TH SA MS WE f FR SU TU TH SA MS WE FR SU TU TH SA MS WE FR SU TU TH g SA MS WE FR SU TU TH SA MS WE FR SU TU TH SA MS WE FR
and they are given in the order that assumes that either the last month is 21 days long, or a day of the week is skipped after the last month, which is what happens except once every 35 or 40 years.
Because a day is skipped before Uayeb each year, and a day is usually skipped after Uayeb when it is 20 days long, it is subject to modifications, causing a skipped day to fall within Uayeb itself, in the same way that the 36-day long months are in order to keep from skipping a Friday, Saturday, or Sunday. In a year in which Uayeb is 20 days long, it will normally come in one of the following seven forms:
S M T W T F S a
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
S M T W T F S b
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20
S M T W T F S c
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20
S M T W T F S d
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20
S M T W T F S e
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20
S M T W T F S f
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20
S M T W T F S g
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20
and in a year in which Uayeb is 21 days long, the seven possible forms of Uayeb are as follows:
S M T W T F S A
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21
S M T W T F S B
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21
S M T W T F S C
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21
S M T W T F S D
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21
S M T W T F S E
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21
S M T W T F S F
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21
S M T W T F S G
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
Thus, using capital letters to represent leap years in which the final month is 21 days long, one cycle of 620 Martian years would look like this:
ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg GAbCd EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe FGaBc CDeFg ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb BCdEf GAbCd EFgAb CDeFg ABcDe FGaBc DEfGa ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf GAbCd DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe FGaBc CDeFg ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb BCdEf GAbCd EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf GAbCd DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe FGaBc DEfGa ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg GAbCd EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf FGaBc DEfGa BCdEf GAbCd EFgAb CDeFg ABcDe EFgAb CDeFg ABcDe FGaBc DEfGa BCdEf GAbCd EFgAb
and then the next cycle begins with B instead of A, and so seven cycles of 620 years begin with the year types A, B, C, D, E, F and G in order. Since April 1, 1987 was a Wednesday, if we begin a 620-year cycle on that day, that means we would start with year type D instead of A as shown above.
However, when no day is skipped, then Uayeb is modified if the preceding month is of the type TH or FR, since there is now no need to skip a day of the week before the last day of the month or the last two days of the month. The following month is modified if it is of the type MS, since now the month needs to actually begin on Monday, as there is no need to skip that day.
Thus, year types f and g, which are the ones that end in TH or FR, are to be replaced with the modified year types x and y when they occur at the end of a 35 or 40 (Martian) year period, or a row in the diagram above, and year type B, which is the one that begins with a month of the type MS, would be replaced with the modified year type Z when it occurs at the beginning of a row. For the same reason, year type B must also be replaced by year type Z, and year type b must be replaced by year type z, whenever it follows a leap year. Thus, a Martian perpetual calendar which shows full calendars for every possible type of Martian year under this system would have not fourteen, but eighteen, possible calendar layouts.
The modified forms of Uayeb are as follows:
S M T W T F S x
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20
S M T W T F S y
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20
and the modified form of Pop when the skipped day shifted from the space between the years is not required is:
S M T W T F S Zz
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31 32 33 34
35 36
Also, no disturbances are shown in the cycle of five years including three Martian leap years. If one is dealing in cycles of 620 Martian years, let alone 4,340 Martian years, some error may accumulate in approximating the odd .592018 Martian days by .6 Martian days. In fact, .592018 times 480 is 367.05116 rather than 372, which is .6 times 620. So we need to omit five leap years in a cycle of 620 years, although in every twentieth such cycle we should only omit four. Note that this does not affect the relationship between the Earth and Mars tropical years, so we simply replace a capital letter in the chart above by its corresponding small letter on four occasions, without changing which letter is used. Let us change the second year in a group of five from a capital letter to a small letter when we do this.
620 years consists of 124 groups of five years, and 124 is only one less than 125, and so a reasonably even spacing of omitted leap years is possible normally; once every twentieth cycle, of course, a completely even spacing is possible, since 124 is 4 times 31. Thus, in a normal cycle of 620 years, of the 124 groups of five years, there will be an omitted leap year in groups 24, 49, 74, 99, and 124, and in every twentieth cycle, the omitted leap years will instead fall in groups 31, 62, 93, and 124.
Thus, the cycle of 620 years which starts on the Martian day corresponding to April 1, 1987 on Earth would actually look like this once those two sets of changes are applied:
DEfGa BCdEf GAzCd EFgAz CDeFg AZcDe FGaBc CDeFg AZcDe FGaBc DEfGa BCdEf GAzCd EFgAz ZCdEf GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa BCdEx FGaBc DefGa BCdEf GAzCd EFgAz CDeFg AZcDe EFgAz CDeFg AZcDe FGaBc DEfGa BCdEf GAzCd DEfGa BCdEf GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa AZcDe FGaBc DEfGa BCdEf GabCd EFgAz CDeFy GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa BCdEx FGaBc DEfGa BCdEf GAzCd EFgAz CDeFg AZcDe EFgAz CDeFg AZcDe FGaBc DEfGa BCdEf GAzCd EFgAz ZcdEf GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa AZcDe FGaBc DEfGa BCdEf GAzCd EFgAz CDeFy GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa BCdEf GAzCd DEfGa BCdEf GAzCd EfgAz CDeFg AZcDe FGaBc CDeFg AZcDe FGaBc DEfGa BCdEf GAzCd EFgAz ZCdEf GAzCd EFgAz CDeFg AZcDe FGaBc DEfGa AZcDe FGaBc DEfGa BCdEf GAzCd EFgAz CDeFg AzcDe
Since the cycles of 620 years begin with A, B, C, D, E, F, and G in order, then, there are three such cycles in the larger cycle of 4,340 years preceding the Martian year starting on this date. Hence, we could call that Martian year the year 1861, which extends the Martian era far enough into the past to ensure positive dates for almost all purposes. 1 Pop of the Martian year 1, would, with that era, correspond to the Earth date corresponding to Julian Day 1,169,178, which is January 13, 1512 B. C., since each 620 year Martian cycle is exactly 425,923 earth days long, and noon on April 1, 1987 is Julian Day 2,446,887.
The real reason for choosing April 1, 1987 as a starting point, however, was to bring the Martian month into correspondence with the Earth month. This means that it is not this calendar, but the other calendar, which is most profoundly affected by the choice of a starting point.
That calendar consists of groups of seven years, four of which have 23 months in them, and three of which have 22 months in them. April cannot be brought into coincidence with the first month of the Martian year, Aries, in years I, IV, or V of the seven-year cycle.
Let us then take the Martian year beginning near April 1, 1987 as being Year VII of a cycle whose relationship to Earth months is given by row 1 in the diagram on the relevant page. Thus, the next year will be Year I of a cycle of type 2. In that calendar, a basic cycle of seven Martian years is related to earth month in six different ways that occur in succession, and a leap day is added after seven such cycles. Thus, the period of this calendar is 294 Martian years, the pattern of leap days recurring every 49 Martian years, and the relationship to Earth months recurring every 42 Martian years.
That, however, assumes that even over that period of time, there is no need to disturb the basic seven-year cycle of four years with 23 months and three years with 22 months at all. If it is reasonable to apply a correction to that basic cycle over such a time, then the shape of the calendar will be changed.
Of course, it may also be reasonable to question whether or not it would be necessary to use a second calendar. Since this calendar brings every Martian day into correspondence with an Earth day, then instead of reproducing the Earth months with another calendar, the Earth months could be reproduced more precisely simply by noting the Earth month in which the corresponding day to the given date falls. Of course, for that purpose, unlike naming the days of the week, one might wish to obtain greater precision by ignoring the adjustments made to ensure that every week has a Friday, a Saturday, and a Sunday. And, of course, as some Earth days are skipped, and must thus share their corresponding Martian day with the day before or after, as well, the equivalent Martian date to a given Earth date may not fall on the same day of the week.
Here is the calendar, then, for the Martian year 1871, which includes most of the Earth years 2006 and 2007. It is a year of type G.
1871
Pop Uo Zip
S M T W T F S S M T W T F S S M T W T F S
1 1 2 3 4 5 6 1 2 3 4
2 3 4 5 6 7 8 7 8 9 10 11 12 13 5 6 7 8 9 10 11
9 10 11 12 13 14 15 14 15 16 17 18 19 20 12 13 14 15 16 17 18
16 17 18 19 20 21 22 21 22 23 24 25 26 27 19 20 21 22 23 24 25
23 24 25 26 27 28 29 28 29 30 31 32 33 34 26 27 28 29 30 31 32
30 31 32 33 34 35 36 35 36 33 34 35 36
Zotz Tzec Xul
S M T W T F S S M T W T F S S M T W T F S
1 2 1 2 3 4 5 6 7 1 2 3 4 5
3 4 5 6 7 8 9 8 9 10 11 12 13 14 6 7 8 9 10 11 12
10 11 12 13 14 15 16 15 16 17 18 19 20 21 13 14 15 16 17 18 19
17 18 19 20 21 22 23 22 23 24 25 26 27 28 20 21 22 23 24 25 26
24 25 26 27 28 29 30 29 30 31 32 33 34 35 27 28 29 30 31 32 33
31 32 33 34 35 36 36 34 35 36
Yaxkin Mol Chen
S M T W T F S S M T W T F S S M T W T F S
1 2 3 1 1 2 3 4 5 6
4 5 6 7 8 9 10 2 3 4 5 6 7 8 7 8 9 10 11 12 13
11 12 13 14 15 16 17 9 10 11 12 13 14 15 14 15 16 17 18 19 20
18 19 20 21 22 23 24 16 17 18 19 20 21 22 21 22 23 24 25 26 27
25 26 27 28 29 30 31 23 24 25 26 27 28 29 28 29 30 31 32 33 34
32 33 34 35 36 30 31 32 33 34 35 36 35 36
Yax Sac Ceh
S M T W T F S S M T W T F S S M T W T F S
1 2 3 4 1 2 1 2 3 4 5 6 7
5 6 7 8 9 10 11 3 4 5 6 7 8 9 8 9 10 11 12 13 14
12 13 14 15 16 17 18 10 11 12 13 14 15 16 15 16 17 18 19 20 21
19 20 21 22 23 24 25 17 18 19 20 21 22 23 22 23 24 25 26 27 28
26 27 28 29 30 31 32 24 25 26 27 28 29 30 29 30 31 32 33 34 35
33 34 35 36 31 32 33 34 35 36 36
Mac Kankin Muan
S M T W T F S S M T W T F S S M T W T F S
1 2 3 4 5 1 2 3 1
6 7 8 9 10 11 12 4 5 6 7 8 9 10 2 3 4 5 6 7 8
13 14 15 16 17 18 19 11 12 13 14 15 16 17 9 10 11 12 13 14 15
20 21 22 23 24 25 26 18 19 20 21 22 23 24 16 17 18 19 20 21 22
27 28 29 30 31 32 33 25 26 27 28 29 30 31 23 24 25 26 27 28 29
34 35 36 32 33 34 35 36 30 31 32 33 34 35 36
Pax Kayab Cumhu
S M T W T F S S M T W T F S S M T W T F S
1 2 3 4 5 6 1 2 3 4 1 2
7 8 9 10 11 12 13 5 6 7 8 9 10 11 3 4 5 6 7 8 9
14 15 16 17 18 19 20 12 13 14 15 16 17 18 10 11 12 13 14 15 16
21 22 23 24 25 26 27 19 20 21 22 23 24 25 17 18 19 20 21 22 23
28 29 30 31 32 33 34 26 27 28 29 30 31 32 24 25 26 27 28 29 30
35 36 33 34 35 36 31 32 33 34 35 36
Uayeb
S M T W T F S
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
and then that same calendar, but showing the Earth date which corresponds to each Martian day:
2006/2007
Pop Uo Zip
S M T W T F S S M T W T F S S M T W T F S
21 26 28 MAR 2 3 4 5 6 7 8
22 23 24 25 26 27 28 5 6 7 8 9 10 11 9 10 11 12 13 14 15
29 30 31 FEB 2 3 4 12 13 14 15 16 17 18 16 17 18 19 20 21 22
5 6 7 8 9 10 11 19 20 21 22 23 24 25 23 24 25 26 27 28 29
12 13 14 15 16 17 18 26 27 28 29 30 31 APR 30 MAY 2 3 4 5 6
19 20 21 22 23 24 25 2 3 7 8 9 10
Zotz Tzec Xul
S M T W T F S S M T W T F S S M T W T F S
12 13 18 19 20 21 22 23 24 25 26 27 28 29
14 15 16 17 18 19 20 25 26 27 28 29 30 JUL 30 31 AUG 2 3 4 5
21 22 23 24 25 26 27 2 3 4 5 6 7 8 6 7 8 9 10 11 12
28 29 30 31 JUN 2 3 9 10 11 12 13 14 15 13 14 15 16 17 18 19
4 5 6 7 8 9 10 16 17 18 19 20 21 22 20 21 22 23 24 25 26
11 12 13 14 16 17 23 27 28 29
Yaxkin Mol Chen
S M T W T F S S M T W T F S S M T W T F S
31 SEP 2 7 12 14 15 16 17 18
3 4 5 6 7 8 9 8 9 10 11 12 13 14 19 20 21 22 23 24 25
10 11 12 13 14 15 16 15 16 17 18 19 20 21 26 27 28 29 30 DEC 2
17 18 19 20 21 22 23 22 23 24 25 26 27 28 3 4 5 6 7 8 9
24 25 26 27 28 29 30 29 30 31 NOV 2 3 4 10 11 12 13 14 15 16
OCT 2 3 4 6 5 6 7 8 9 10 11 17 18
Yax Sac Ceh
S M T W T F S S M T W T F S S M T W T F S
20 21 22 23 26 27 4 5 6 7 8 9 10
24 25 26 27 28 29 30 28 29 30 31 FEB 2 3 11 12 13 14 15 16 17
31 JAN 2 3 4 5 6 4 5 6 7 8 9 10 18 19 20 21 22 23 24
7 8 9 10 11 12 13 11 12 13 14 15 16 17 25 26 27 28 29 30 31
14 15 16 17 18 19 20 18 19 20 21 22 23 24 APR 2 3 4 5 6 7
21 22 23 24 25 26 27 28 MAR 3 8
Mac Kankin Muan
S M T W T F S S M T W T F S S M T W T F S
10 11 12 13 14 17 18 19 23
15 16 17 18 19 20 21 20 21 22 23 24 25 26 24 25 26 27 28 29 30
22 23 24 25 26 27 28 27 28 29 30 31 JUN 2 JUL 2 3 4 5 6 7
29 30 MAY 2 3 4 5 3 4 5 6 7 8 9 8 9 10 11 12 13 14
6 7 8 9 10 11 12 10 11 12 13 14 15 16 15 16 17 18 19 20 21
13 14 15 17 18 19 20 22 22 23 24 25 26 27 28
Pax Kayab Cumhu
S M T W T F S S M T W T F S S M T W T F S
29 31 AUG 2 3 4 5 6 7 8 12 13
5 6 7 8 9 10 11 9 10 11 12 13 14 15 14 15 16 17 18 19 20
12 13 14 15 16 17 18 16 17 18 19 20 21 22 21 22 23 24 25 26 27
19 20 21 22 23 24 25 23 24 25 26 27 28 29 28 29 30 31 NOV 2 3
26 27 28 29 30 31 SEP 30 OCT 2 3 4 5 6 4 5 6 7 8 9 10
2 3 7 8 9 10 11 12 13 14 16 17
Uayeb
S M T W T F S
18 19 20 21 22 23 24
25 26 27 28 29 30 DEC
2 3 4 5 6 7 8
Given that there are omitted Earth dates that correspond to no date upon Mars, one could speak of June 15, 2006 as being 34 1/2 Zotz, 1871; but in the usual case, when the omitted date is not within a month, only between two consecutive months, one can simply refer to April 4, 2006 as a conventional-sounding 37 Uo, 1871. Which date happened to be tomorrow as I wrote these words.
Certainly, it is possible to consider some further modifications to this calendar. For example, instead of simply moving the day of the week that is skipped a day or two before or after the transition between months, the lengths of the months could be varied instead. Also, while every week needs to have a Friday, a Saturday, and a Sunday, one could limit the distance the day that is skipped is moved by dropping the requirement that every week have a distinct Friday, Saturday, and Sunday.