Re: Why we should reform the Calendar
*The Minimum-Displacement Leapyear Rule:* This is a leap-week leapyear-rule. The common (non-leap) year is 364 days long. A leapyear is 364 + 7 = 371 days long. The leapweek is added at the end of the year, becoming part of that year Epoch: Gregorian January 2, 2017 is this calendar's start, being this calendar's January 1, 2017.. *Variable: * D D stands for "displacement". Though this definition isn't needed for the specification of this leapyear-rule, displacement is a change or difference in the relation between date and ecliptic longitude. Actually the progress of a mean-year, or an approximation to one, usually stands in for ecliptic longitude in a leapyear-rule. D, here, is the difference between the current year's displacement from the year's desired relation between date & ecliptic longitude (where ecliptic longitude is represented by the progress of the mean-year). *Constants:* 1. Dzero is the starting value of D, the value of D at the calendar's epoch. (The epoch is the time at which the calendar is defined to start). 2. Y is the length of the leapyear-rule's mean-year (I sometimes call it the "reference-year" too). For the value of Dzero, I offer -.6288 or 0. Of those two, I recommend -.6288 (...for reasons I'll get to later in this post.) A Dzero of -.6288 means that the year is, at its epoch, displaced by -.6288 days from its desired relation of date & season. For the value of Y, I recommend 365.24217, the approximate number of mean solar days in a mean tropical year (MTY). Dzero & Y are the two adjustment-parameters that I spoke of in a previous post. *Year-End Change in D:* At the end of a calendar year (whether common or leap), the value of D changes by an amount equal to Y minus the length of that year in days. If that change would otherwise result in a D value greater than +3.5, then 7 days are added to the end of that year, before implementing the paragraph before this one. ...making that year a leapyear. [end of Minimum-Displacement leapyear-rule] In this way, the value of D is kept within the limits of -3.5 days to + 3.5 days. D is a good measure of the calendar's displacement from its desired date/season relation defined by Dzero. The -.6288 value of Dzero is consistent with a desired relation of calendar-date and ecliptic-longitude (...where ecliptic-longitude is represented by the progress of the 365.24217 day mean-year) that is the midpoint of the extremes of the values that that relation had between January 1, 1950 and January 1, 2017. ...in order that the calendar's center of displacement-oscillation be the average of its variation-extremes since January 1, 1950. ...so that the calendar's date-season relation will stay close to where it has been during the experience of currently-living humans. Though I like the ISO WeekDate calendar, and it's said that it has a good chance of eventually displacing Roman-Gregorian, via gradually-increasing usage, my proposal is a calendar using the 30,30,31 quarters, and the Minimum-Displacement leapyear-rule, with Dzero = -.6288, and with Y = 365.24217. I should add that calculation, with the Minimum-Displacement rule, of durations, day-of-the-week, & displacements are no more difficult than the same calculations with the Gregorian leapyear-rule. And determination of whether a particular far-distant year is a leapyear is no more difficult than those calculations. ...and of course the determination of whether the *next* year is a leapyear is just a matter of directly applying the leapyear-rule, as defined above. . ..and of course, any time when the current year is a leapyear, that fact will be amply announced long before the end of that year. Michael Ossipoff approx. 26N, 80W --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Why we should reform the Calendar
On Sun, Jan 29, 2017 at 2:41 PM, Robert Kellogg <rkell...@comcast.net> wrote: > Michael goes off looking for the ideal tropical year There isn't an "ideal tropical year", but, as a choice for a leapyear-rule's mean-year, the length of the mean tropical year (MTY) is best for year-round reduction of longterm calendar-drift. ...and the average of the lengths of the March & September Equinox tropical years (I'll call that the Average Equinox Year (AEY) ) is a compromise between the vernal equinoxes of the North & the South. > , perhaps ignoring effects of the earth's nutations. > Of course. The nutations are small in amplitude & period. They aren't part of calendar rules. The mean equinox (nutations averaged-out) is the one that is meant when the equinox is spoken of with regard to calendars. > I'll still take the one of 1900, most importantly because it defines the > SI second. The SI second was defined as 1/86,400 of a mean solar day, for some year in the early 19th century. I don't remember exactly what year that was. 1820? 1840? 1850? Evidently it isn't practical to update the length of the SI second, but that doesn't mean that calendars have to be based on the ephemeris day, or atomic day, consisting of 86,400 SI seconds, when that's known to be different from today's mean solar day. That's why I suggest 365.24217 instead of 365.24219 for the length of the mean tropical year (MTYI. It makes sense to base a calendar leap-year rule's mean-year on the actual length of a tropical-year (whichever one we want to use) on the length of that tropical year in* today's* mean days. > > > So, contemplating changing the year is non trivial. Evidently there must be some reason why it would be impractical to update the length of the SI second. But it isn't necessary to call a MTY 365.24219 days, when it's really 365.24217 mean days long. ...for the purposes of a calendar leapyear rule. There's inevitable inaccuracy due to rounding-off, and due to gradual change in the lengths of all the tropical years, including the MTY. But that doesn't mean we have to intentionally add avoidable error. > Contemplating decoupling UTC from the rotation of the earth (ie necessity > of being within .9 sec of UT1) likewise has significant consequences. > Let's let the IAU chart the future of time. Sure, but it isn't necessary to base a calendar on a day that isn't today's mean solar day. Michael Ossipoff > Dennis and Ken, if you're listening to this discussion, please chime in. > > > On 1/29/2017 12:27 PM, sundial-requ...@uni-koeln.de wrote: > >> Send sundial mailing list submissions to >> sundial@uni-koeln.de >> >> To subscribe or unsubscribe via the World Wide Web, visit >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> or, via email, send a message with subject or body 'help' to >> sundial-requ...@uni-koeln.de >> >> You can reach the person managing the list at >> sundial-ow...@uni-koeln.de >> >> When replying, please edit your Subject line so it is more specific >> than "Re: Contents of sundial digest..." >> >> >> Today's Topics: >> >> 1. Re: Why we should reform the Calendar (Michael Ossipoff) >> >> >> -- >> >> Message: 1 >> Date: Sun, 29 Jan 2017 12:27:56 -0500 >> From: Michael Ossipoff <email9648...@gmail.com> >> To: Dan-George Uza <cerculdest...@gmail.com> >> Cc: sundial list <sundial@uni-koeln.de> >> Subject: Re: Why we should reform the Calendar >> Message-ID: >> <CAOKDY5Aes1J6NFKjxXvQ_WxW1x1mfGGq9+F7wFjX72GRaiOLTQ@mail. >> gmail.com> >> Content-Type: text/plain; charset="utf-8" >> >> >> 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
Re: Why we should reform the Calendar
Michael goes off looking for the ideal tropical year, perhaps ignoring effects of the earth's nutations. I'll still take the one of 1900, most importantly because it defines the SI second. Yes, I recognize that we've now accepted the second using cesium (TAI = Atomic Time International), and Universal Time Coordinated (UTC) where we keep the rate of the SI second, but accommodate the vagaries of an erratic but slowing earth (UT1) by throwing in a leap second every now and then. We should ponder terrestrial dynamic time (TDT) that uses the SI second, has a unit of day as 86400 SI seconds at mean sea level. The "mean sea level" needs to be thrown in since as we move away from the earth (as our GPS satellites), time moves faster thanks to Einstein's General Relativity. So, contemplating changing the year is non trivial. Contemplating decoupling UTC from the rotation of the earth (ie necessity of being within .9 sec of UT1) likewise has significant consequences. Let's let the IAU chart the future of time. Dennis and Ken, if you're listening to this discussion, please chime in. On 1/29/2017 12:27 PM, sundial-requ...@uni-koeln.de wrote: Send sundial mailing list submissions to sundial@uni-koeln.de To subscribe or unsubscribe via the World Wide Web, visit https://lists.uni-koeln.de/mailman/listinfo/sundial or, via email, send a message with subject or body 'help' to sundial-requ...@uni-koeln.de You can reach the person managing the list at sundial-ow...@uni-koeln.de When replying, please edit your Subject line so it is more specific than "Re: Contents of sundial digest..." Today's Topics: 1. Re: Why we should reform the Calendar (Michael Ossipoff) -- Message: 1 Date: Sun, 29 Jan 2017 12:27:56 -0500 From: Michael Ossipoff <email9648...@gmail.com> To: Dan-George Uza <cerculdest...@gmail.com> Cc: sundial list <sundial@uni-koeln.de> Subject: Re: Why we should reform the Calendar Message-ID: <caokdy5aes1j6nfkjxxvq_wxw1x1mfggq9+f7wfjx72graio...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" 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
Re: Why we should reform the Calendar
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!"
Re: Why we should reform the Calendar
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
RE: Why we should reform the Calendar
Hear, hear!! From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Dan-George Uza Sent: Saturday, January 28, 2017 12:38 PM To: sundial@uni-koeln.de Subject: Why we should reform the Calendar A bit off topic, but I enjoyed this quite a lot! https://youtu.be/EcMTHr3TqA0 Dan --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Why we should reform the Calendar
A bit off topic, but I enjoyed this quite a lot! https://youtu.be/EcMTHr3TqA0 Dan --- https://lists.uni-koeln.de/mailman/listinfo/sundial
