Hello Rod, I just added a little MP4 video from the last leap second to my homepage. So you can see how it works.
Look here: www.sonnenuhren-lindner.de <http://www.sonnenuhren-lindner.de> Regards. Peter Von: sundial [mailto:sundial-boun...@uni-koeln.de] Im Auftrag von Richard Langley Gesendet: Montag, 30. Januar 2017 00:02 An: rodwall1...@gmail.com Cc: sundial list <sundial@uni-koeln.de> Betreff: Re: Time question on GPS TIME and leap second. Yes. The navigation message transmitted by GPS satellites includes the current leap second offset so a receiver can compute and display correct UTC. -- Richard Langley Sent from my iPhone On Jan 29, 2017, at 6:05 PM, rodwall1...@gmail.com <mailto:rodwall1...@gmail.com> <rodwall1...@gmail.com <mailto:rodwall1...@gmail.com> > wrote: Hi all, Was just listening to the CrowdScience on time. Thanks to whoever posted the link to it. CrowdScience indicated that a leap second was not added for the GPS. They also indicated that the GPS gives us UTC time. Question: The UTC time that the GPS gives. Does that have the leap second added? Thanks, Regards, Roderick Wall. ----- Reply message ----- From: "Michael Ossipoff" <email9648...@gmail.com <mailto:email9648...@gmail.com> > To: "Robert Kellogg" <rkell...@comcast.net <mailto:rkell...@comcast.net> > Cc: "sundial list" <sundial@uni-koeln.de <mailto:sundial@uni-koeln.de> > Subject: Why we should reform the Calendar Date: Mon, Jan 30, 2017 8:00 AM On Sun, Jan 29, 2017 at 2:41 PM, Robert Kellogg <rkell...@comcast.net <mailto: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 <mailto:sundial-requ...@uni-koeln.de> wrote: > >> Send sundial mailing list submissions to >> sundial@uni-koeln.de <mailto: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 <mailto:sundial-requ...@uni-koeln.de> >> >> You can reach the person managing the list at >> sundial-ow...@uni-koeln.de <mailto: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 <mailto:email9648...@gmail.com> > >> To: Dan-George Uza <cerculdest...@gmail.com <mailto:cerculdest...@gmail.com> > >> Cc: sundial list <sundial@uni-koeln.de <mailto:sundial@uni-koeln.de> > >> Subject: Re: Why we should reform the Calendar >> Message-ID: >> <CAOKDY5Aes1J6NFKjxXvQ_WxW1x1mfGGq9+F7wFjX72GRaiOLTQ@mail. >> gmail.com <http://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, 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 <mailto: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 <mailto: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 >>>> >>>> >>>> >>>> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: <https://lists.uni-koeln.de/mailman/private/sundial/attachme >> nts/20170129/9cea9958/attachment.html> >> >> ------------------------------ >> >> Subject: Digest Footer >> >> _______________________________________________ >> sundial mailing list >> sundial@uni-koeln.de <mailto:sundial@uni-koeln.de> >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> ------------------------------ >> >> End of sundial Digest, Vol 133, Issue 27 >> **************************************** >> >> > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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