Here are two (unimportant) objections to the Nearest-Monday year-start system:
1. It's based on the Gregorian leapyear-rule, meaning that it isn't self-contained & free-standing. Mostly an aesthetic objection, and I don't consider it important. 2. It inherits certain properties of the Gregorian Calendar, which could otherwise be adjustable, choose-able. This, too, I consider only an aesthetic objection. Here are the properties that I refer to: The Gregorian leapyear-rule was designed to minimize the date's variation at the (northern) Vernal Equinox, the March equinox. We often hear it said that the mean tropical year is the time from one March equinox to the next. Not so. That's because the length of a tropical year depends on at what point of the ecliptic it's measured. A tropical year is a seasonal year, the time during which the center of the sun leaves & returns to some particular point of the ecliptic. That duration is different, depending on the point of the ecliptic at which it's measured. That's because the Earth's orbit is continuously changing, due to perturbation by other planets, mostly Jupiter. So, for example, the following tropical years have different durations: The March Equinox year, the September Equinox year, the June Solstice year, and the December Solstice year. Leapyear-rules try to achieve some desired "mean year". The Gregorian leapyear-rule's mean-year is 365.2425 days. Probably mean solar days, I assume. As I said, the Gregorian's mean-year is intended to approximate the March Equinox year. A mean solar day is the duration between meridian-transits of the mean sun. The mean sun is a fictitious sun that goes around the celestial equator at a constant rate, coinciding at the equinoxes with another fictitious sun that goes around the ecliptic at a constant rate and coincides with the real sun at aphelion & perihelion. Often the length of (various kinds of) a tropical year is given in ephemeris days (defined in terms of planetary motions), also callled atomic days.(when defined in terms of atomic clock measurements). The length of an ephemeris day was fixed in the early 19th century. But, since then, the length of the day has increased a bit, and so the ephemeris day no longer matches the mean solar day. For example, we often hear it said that a mean tropical year is 365.24219 days. But that's ephemeris days. According to a Wikipedia article (calendarists that I've spoken with haven't expressed disagreement with it), a mean tropical year is actually currently about 365.24217 mean solar days. The length of the mean tropical year is the (current value of the) arithmetic mean of the lengths of the tropical year measured at all the points of the ecliptic. So, if you calculated two Earth orbits, accounting for planetary perturbations. recording the time at many different points of the ecliptic, and then used those times to calculate the tropical year with respect to those many points of the ecliptic, and then, over one circuit around the ecliptic, numerically integrated the tropical-year-length, with respect to ecliptic longitude, and then divided by 2 pi radians ( = 360 degrees), that would give you the length of a mean tropical year. As I said, according to Wikipedia, it's currently about 364.24217 days. So, anyway, the Gregorian leapyear rule's mean-year, of 365.2425 days is intended as an approximation of the March equinox year of about (it seems to me) 365.24239 days. It's understandable that they chose to favor the Vernal Equinox year. The equinoxes are the time when the solar declination is changing fastest, and when the season is changing fastest. Problem: The Northern Hemisphere's Vernal Equinox isn't the Southern Hemisphere's Vernal Equinox. The Vernal Equinox, near the beginning of Spring, is a revered, honored & celebrated time. But why should the people of the Southern Hemisphere celebrate the *northern* Vernal Equinox? In 1582 that wasn't a problem for Europeans. But this is a different century now. In this century, choosing the northern Vernal Equinox as the basis for the calendar's mean year is more than a little north-chauvinistic and inegalitarian. So I'd prefer to use an approximation to the mean tropical year, instead of the March equinox year, as a leapyear-rule's mean year. That's what my leapyear-rule proposal does. (I'll get to that soon). Another fair choice, another good compromise between North & South, would be a mean-year length that's the arithmetic average of the March & September Equinox years. Some calendarists like the June Solstice tropical year, as a mean-year for a leapyear-rule. That's because the we're now only about a millennium into a roughly 10,000 year period during which the length of the June Solstice year will change remarkably little--not enough to cause any significant calendar-displacement with respect to the seasons.. To quote one calendarist: "Welcome to the 1st millennium of the Age of the June Solstice Year!" So the current period of remarkable stability of the length of the June Solstice year has only been in effect since roughly the time of the Battle of Hastings. So of course the June Solstice tropical year has great appeal as the mean-year for a leapyear-rule. And that wouldn't be unfair to the South, because the Winter Solstice is celebrated as much as the Summer Solstice. Though my calendar-proposal is to use the mean tropical year, or the arithmetic average of the March & September Equinox years as the mean year for a leapyear-rule, I'd have no objection at all to the use of the June Solstice year, which has great appeal. The point is that we can choose what tropical year we use for a mean year for a calendar's leapyear-rule. But if we use the Nearest-Monday year-start rule, we're inheriting the Gregorian's use of the March Equinox year as the tropical year that the calendar's mean year approximates. That isn't really a problem, but it would be nice to make that choice for ourselves--as my Minimum-Displacement leapyear-rule (defined later) does. The other things is that the Gregorian's 365.2425 day mean-year, being more approximate, results in more drift (with respect to its intended tropical year length) than would a more precise approximation. And when the calendar's relation between date & ecliptic longitude oscillates, in the leapyear-system, about what central date/season relation does it oscillate? Wilth the Gregorian, and hence with Nearest-Monday, that's out of our hands, decided for us. I'm not saying that that's a problem either. It's just that it would be *nice* to have the luxury of choosing, for ourselves, 1) what tropical year we want the calendar's mean-year to approximate; and 2) what date/season relation we want for the calendar's center of oscillation. The Minimum-Displacement leapyear-rule allows the luxury of making our own choice of those two adjustment-parameters. This posting is already very long, and so I'll save the Minimum-Displacement leapyear-rule for a (immediately subsequent) next posting. Michael Ossipoff I seems to me that the March Equinox tropical year is something like 365.24239 On Sat, Jan 28, 2017 at 8:54 PM, Michael Ossipoff <email9648...@gmail.com> wrote: > I don't think it's really off-topic, because, with sundials, we're > interested in the EqT, which is given in terms of the calendar's dates. > > Though Gorman is a comedian, he's obviously given the matter some serious > consideration, and I perceive some serious interest in calendar-reform. > > But I have a few disagreements with his proposal: > > > > *1. Blank Days:* > Gorman proposes a "fixed calendar", a calendar that will be the same for > every year. I have no objection to that. After all, so far as we know > (except for each year setting a new record for increasing global warming) > what we can expect from each year, nature-wise, is really the same. So, why > should two successive years have different calendars, with different dates > having different days-of-the-week? > > So far so good. There are two ways proposed for achieving a fixed > calendar: > > *1. Blank Days:* > > A fixed calendar must have a number of days that's a multiple of 7, That's > what enables each calendar to start on the same day of the week, allowing > every date to have a day-of-the-week that doesn't change from year to year. > So Gorman would make one of the 365 days a "blank day", a day that isn't a > day of the week. Then the days-of-thes-week would resume after that day. so > the year would have only 364 days that are days of the week. That being a > multiple of 7, each year will start on the same day of the week, as desired. > > Problem: I'm sorry, but it doesn't make any sense for the day after a > Saturday to be anything other than a Sunday. ...or for there to be an > intervening day between a Saturday & a Sunday. > > Speaking for myself, I completely reject "blank-days". And I'm not the > only one. Elizabeth Achellis, over several decades, up to around 1955, > proposed a fixed calendar with blank-days. The League of Nations, and later > the U.N. were giving serious consideration to it, and it might have been > accepted, except for the strong opposition to the blank-days, > > A compromise was offered to Achellis: A leap-week (described in the next > section below), to achieve a fixed calendar. She wouldn't accept that > compromise, and her proposal was indefinitely tabled around 1955, and never > got anywhere since. You could say that the blank-days were the Achilles' > heel of Achellis' calendar proposal. > > > > *Leap-Week:* > So a 364 day common (non-leap) year achieves a fixed calendar, because 364 > is divisible by 7. What about the 365th day? Well, we could deal with it > the same way we deal with the fact that the 365 day year is shorter than > the 365.24217 day Mean Tropical Year (MTY)...by occasionally lengthening a > year, to periodically compensate for the length-mismatch. So we'd deal with > the short common year just as we do now. > > So, what we do is have a 364-day common year, and (by using a leap-year > rule that I'll talk about later), when that 364-day common year gets about > half a week out-of-step with the seasons, we add a leapweek, to set that > displacement back. > > Gorman didn't talk about the leapyear-system, and we can presume that he > meant to use the existing Gregorian leapyear system, which would be fine, > for a leapday calendar such as he proposes. But for a leapweek calendar, > which is what I (and many others) propose, a new leapyear system is > required. No problem. I'll get to that after I discuss my disagreements > with Gorman's proposal. > > Summary: A fixed calendar should be achieved via a leapweek, instead of by > blank-days. If Achellis had agreed to that, we might be using her calendar > right now. > > *2. Thirteen Months:* > > Really, the only reason for a reform calendar to have months, is for > continuity & familiarity with our current Roman-Gregorian Calendar. > > For example, Elizabeth Achellis's *World Calendar *had, in each quarter, > months with the following lengths: 31,30,30. Having 12 months, with 30 or > 30 or 31 days, means that the calendar is familiar, looks familiar, and it > means that the dates in the new calendar have really the same seasonal > meaning as the dates in the old calendar. > > Achellis' 31,30,30 quarters achieves that. But there are other proposals > of a calendar with > 30,30,31 quarters. The advantage?: > > 1. The 30,30,31 calendar's months' start-days never differ by more than a > day, from those of our current Roman months, when both month-systems start > on the same day. Achellis' 31,30,30 quarter system can differ by at least > twice as much. > > 2. The 30,30,31 quarters divide the weekdays most equally between the > months of the quarter. > > So, if you're going to have months at all (and that's for continuity & > familiarity), then you want 12 months, of 30 & 31 days. Preferably the > 30,30,31 quarters. > > With 13 months of 28 days, the dates wouldn't have anything like the > seasonal meaning that they do now. Continuity, familiarity, and the > justification for having months at all, would be lost. > > The 30,30,31 quarter system is an improvement over our current Roman > months, because the months are much more uniform. That allows much > meaningful & accurate monthly statistics. > > But suppose you want something more radical (as is Gorman's 28X13 system): > > In that case, just don't have months, because their continuity & > familiarity purpose would be lost anyway. Use the WeekDate system. > > No months. > > Weeks are numbered. > > Here's today's date in the (currently internationally widely-used) ISO > WeekDate calendar: > > 4 Saturday > > That means Saturday of the 4th week. > > Actually, because not all countries and languages call the da > > ys of the week by the same names, here is how the ISO (International > Standards Organization) words today's date. > > 2017W046 > > The "W" indicates that the WeekDate system is being used. > > The "04" denotes the 4th week. > > The "6" denotes the 6th day of that week. > > (The ISO WeekDate Calendar uses a week (and therefore a year) that begins > on a Monday, probably so that the weekend won't be split in half.) > > The ISO WeekDate Calendar is, as I said, widely used internationally, by > Companies & Governments, for their planning of business & governmental > dates & events. ...making it easy to plan them in advance once, and then > leave them, because it's a fixed calendar. Of course the resulting dates > then have to be eventually translated into Roman-Gregorian dates. > > > ...but they wouldn't have to, if we adopted the ISO WeekDate calendar as > our civil calendar, worldwide. > > ISO WeekDate has the great advantage of use-precedent. ...lots of it. > > I personally like the ISO WeekDate as the best calendar-reform proposal. > > But, recognizing that many people wouldn't want to give up the months, and > would want to keep them for familiarity & continuity, the 30,30,31 > month-system could be a good alternative proposal, if ISO WeekDate isn't > accepted. > > But it has been argued that ISO WeekDate is so convenient, and already so > widely-used, that it could easily edge-out the Roman-Gregorian Calendar, > from the bottom up, by increasingly wide use, if companies & government > start using it so much that the public start finding it convenient to use > it too. > > So those are my two disagreements with Gorman's proposal, and my > alternative suggestions. > > But I should comment on the leapyear rule. Actually, the ISO WeekDate > Calendar deals with that in a really easy, natural, simple & obvious way. > > Each ISO WeekDate year starts on whatever Monday is closest to the > Gregorian January 1st of that year. So, for example, this year, 2017, the > Gregorian year started on a Sunday. So the nearest Monday to Gregorian > January 1st was January 2nd. That Monday, Gregorian January 2nd, is the day > on which ISO WeekDate 2017 started. > > As I said, today, in the ISO WeekDate Calendar, is: > > 4 Saturday > > (or 2017W046) > > That way of defining the start of the ISO WeekDate year (the Monday closes > to Gregorian January 1st) is called the Nearest-Monday year-start system. > > Note that the Nearest-Monday year-start system doen't have to mention > leapyears or leapweeks at all. It's *effectively* a leapweek calendar, > because some of the years have 53 weeks instead of 52. But the simple > Nearest-Monday year-start rule doesn't need to mention leapyears or > leapweeks. > > Not only is it used with the ISO WeekDate Calendar, but of course it could > also be used with a 30,30,31 quarters calendar too. > > Calendar reform advocates propose all manner of different leapyear > systems. But there's nothing wrong with the Nearest-Monday year-start > system, and conversations have suggested to me that Nearest-Monday would be > the favorite way to make a fixed calendar. > > In fact, with Nearest-Monday, the maximum displacement of dates with > respect to seasons, is barely more than the ideal minimum that could be > achieved by the fanciest leapyear system. > > I also propose a fancier, deluxely-adjustable system, but I won't try your > patience with that here, because Nearest-Monday is entirely good enough, > and is the system with obviously by far the best acceptance-potential. > > Michael Ossipoff. > > > > > > > On Sat, Jan 28, 2017 at 3:38 PM, Dan-George Uza <cerculdest...@gmail.com> > wrote: > >> A bit off topic, but I enjoyed this quite a lot! >> >> https://youtu.be/EcMTHr3TqA0 >> >> Dan >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> >
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