Re: Equinox, Full Moon and Easter
For that matter, why are we even still using the Roman-Gregorian Calendar? (Roman months with Gregorian leap-year-rule) . There are many alternative calendar proposals, but, among all of those that keep weeks, the minimal, most convenient and easy calendar is a WeekDate calendar: . The weeks of the year are numbered, and the date consists of the week-number and the day-of-the-week. . The most un-arbitrary WeekDate proposal, is South-Solstice WeekDate: . Today’s date, in South-Solstice WeekDate, is: . 13 Sa . …Saturday of the 13th week of the calendar-year that started with the Monday that started nearest to the South-Solstice. - Of course, like the French-Republican Calendar of the 18th century, that year-start rule depends on an annual astronomical observation (or orbital-calculation). . An arithmetical rule is considered more convenient. For example, our Gregorian leapyear-rule is based on an arithmetical approximation to the March equinox. . South-Solstice WeekDate can also be defined with an arithmetical year-start rule, based on an arithmetical approximation to the South-Solstice, based on an assumption that a South-Solstice occurs exactly every 365.2422 days, starting from (say) the actual South-Solstice of 2017. . So, that approximated South-Solstice is used instead of the actual South-Solstice. The calendar year starts with the Monday that starts closest to the approximated South-Solstice defined in the previous paragraph. There’s a WeekDate calendar that’s actually in wide international use by governments and companies: . The International Standards Organization WeekDate calendar (ISO WeekDate Calendar): . The calendar year starts with the Monday closest to Gregorian January 1st. . A bit arbitrary, and dependent on the old Roman-Gregorian Calendar, but it’s already in wide use, and its software is already widely-distributed. . I’ve found that many people prefer (at least as a first reform-proposal) ISO WeekDate to South-Solstice WeekDate, because of the familiarity of Gregorian January 1st as the basis for year-start. -- Both of those WeekDate proposals, South-Solstice WeekDate and ISO WeekDate, of course start every year on a Monday. With every year starting on the same day-of-the-week, then every calendar-year is identical, other than the fact that every 5th or 6th year automatically has a 53rd week. That would bring a tremendous simplicity for scheduling of annual events and holidays. For example, if desired, as come calendarists propose, Easter could be defined as a particular Sunday date, such as 13 Su or 14 Su. Always on a Sunday, and its date would be the same each year. . The day-of-the-week for a distant future appointment would never be in question, because the day-of-the-week is _part of_ the date. . With Roman-Gregorian, the day-of-the-month of course changes each day, and people usually look it up, referring to a printed or digital calendar. With a WeekDate calendar, if you know the day-of-the-week, then you know the date. For example, today the week-number has been 13 for some days, ever since last Monday, and it will remain so until next Monday. So, because yesterday was 13 F, today is 13 Sa. . Durations, too, are easier to determine with WeekDate, compared to with the Roman months. --- Someone could argue that, due to millennia of use, the Roman months tell us something about the season. But there’s nothing inherently more seasonal or natural about the Roman months. In fact, South-Solstice WeekDate gives good seasonal information without millennia of familiarity: . We’re now in week 13. At the end of week 13, we’re roughly a quarter-year after the South-Solstice, meaning that one would expect the end of week 13 to be near the Northward (March) Equinox. (…but not exact, because the calendar-year starts, not on the South-Solstice, but rather on the nearest-Monday, as specified above.) . So the South-Solstice WeekDate week-number is a rough but good indication of the solar ecliptic longitude. . Michael Ossipoff . 13 Sa (South-Solstice WeekDate Calendar) 1551 UTC --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Dear Fabio, Many thanks for your follow-up. I look forward to hearing more when you get your book back. I wonder how many people know how difficult it is to define 'Sunday'!! It is possible to define Sunday so that, sometimes, half the planet has Easter after one full moon and the other half of the planet has Easter after the next full moon! Ciao Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Dear Frank the replay at your question is not easy. I see some ways to find it: - one is exhaustive, few lines of software could check how many times the naive rule is verified in the whole cycle. It isn't very smart but it may be useful to verify the other points - to disassemble the algorithm finding where and when it intervenes to shift the date - reformulate an approach to find when the sunday overlap the canonical full moon but I think I would find myself in the previous point, with the formulation of epacts of Clavius - to consult the book of Tempesti where there are many kind of tables and considerations on this matter, may be the answer is already written. At first I think to follow the last point, unluckily I lent the book and it come back to me in the next days, I'll come back on the matter as soon as the book returns to my hands. Yesterday I went to sleep thinking about the 3rd point, obviously I didn't solve my question but I dreamed my 'Sunday': I was going to an heliodrome with an ice cream :-) ciao Fabio Il 22/03/2019 17:02, Frank King ha scritto: Dear Fabio, I think the Spencer-Jones algorithm is now widely accepted as defining when Easter will be observed (by both the Roman Catholic Church and the Anglican Church for the foreseeable future). What is interesting is just how often it produces the same date as the naive rule of 'the first Sunday after the first full moon after the equinox'. This year is clearly an exception because the algorithm and the naive rule give different answers. Do you know how often the algorithm and the naive rule differ? You are allowed to choose your own defintion of 'Sunday'! Ciao Frank -- Fabio Savian fabio.sav...@nonvedolora.it www.nonvedolora.eu Paderno Dugnano, Milano, Italy 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Dear Fabio, I think the Spencer-Jones algorithm is now widely accepted as defining when Easter will be observed (by both the Roman Catholic Church and the Anglican Church for the foreseeable future). What is interesting is just how often it produces the same date as the naive rule of 'the first Sunday after the first full moon after the equinox'. This year is clearly an exception because the algorithm and the naive rule give different answers. Do you know how often the algorithm and the naive rule differ? You are allowed to choose your own defintion of 'Sunday'! Ciao Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Please unsubscribe me On Fri, Mar 22, 2019 at 5:00 AM fabio.sav...@nonvedolora.it < fabio.sav...@nonvedolora.it> wrote: > Dear Frank, > > ... ANSI Standard Easter, I missed it, I hope none of the international > authorities for the standards read this mailing-list :-) > > Even Gauss took care of it but his algorithm doesn't manage some > exceptions. > > For those interested in the matter: > Algorithm to calculate the date of Easter, by Spencer Jones, from his book > General Astronomy, pages 73-74, edition of 1922. > Published again in the Journal of the British Astronomical Association, > vol. 88, page 91, december 1977. > Here it is reported that the algorithm was defined on 1876 and it appeared > in the Butcher's Ecclesiastical Calendar. > Unlike the algorithm of Gauss, this hasn't exceptions and it runs for the > Gregorian Calendar, starting from 1583. > > The limits of the dates are march 22 and april 25. > The dates of Easter have a cycle of 5,700,000 years. > The most frequently date is april 19. > > Example for 2019: > A=5, B=20, C=19, D=5, E=0, F=1, G=6, H=29, J=4, K=3, L=1, M=0, N=4, P=20 > N=4 that is april, P+1=21 > > The Orthodox Easter follows the Julian Calendar, the algorithm is: > > > The cycle of the dates of the Julian Easter is 532 years. > > Example for 2019: > A=3, B=3, C=5, D=20, E=4, F=4, G=14 > N=4 april, G+1=15, in the Gregorian Calendar 15+13=28 > > ciao Fabio > > > Il 21/03/2019 15:35, Frank King ha scritto: > > Dear Roger, > > I note that you say: > > > My reference on this topic is The Sun in > the Church by J L Heilbron. > > He is pretty sound on this and, as early > as page 3, notes that the time of the > equinox and the time of full moon depend > where you are on the planet. He adds, > "as, of course does Sunday". > > If everyone used the Julian Date then > they might all agree on the instant of > the equinox and the instant of full > moon but it seems most unlikely that > they would have similar agreement as > to what is meant by "Sunday". > > It takes 48 hours from the start of a > given Sunday, just to the west of the > International Date Line, to the end of > the same Sunday, just to the east of > the Line. > > Fabio has pointed out that Rome and > Jerusalem have been suggested as > candidate places for defining a > Canonical Sunday. I too have read > this but I don't know where the > supposed primary source is. > > I think Fabio's explanation is the > most plausible. In essence, you > define an algorithm (albeit one > that is a bit suspect) and impose > a kind of ANSI Standard Easter :-) > > As a former colleague once told me: > "The great thing about having Standards > is that there are so many of them." > > You are one of the most-westerly > subscribers to this list so I think > a Bailey-Standard Easter would be > worth lobbying for. > > You might thereby become a noted > Holy Man. Be careful! > > Very best wishes > > Frank > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > Fabio savianfabio.sav...@nonvedolora.itwww.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Dear Frank, ... ANSI Standard Easter, I missed it, I hope none of the international authorities for the standards read this mailing-list :-) Even Gauss took care of it but his algorithm doesn't manage some exceptions. For those interested in the matter: Algorithm to calculate the date of Easter, by Spencer Jones, from his book General Astronomy, pages 73-74, edition of 1922. Published again in the Journal of the British Astronomical Association, vol. 88, page 91, december 1977. Here it is reported that the algorithm was defined on 1876 and it appeared in the Butcher's Ecclesiastical Calendar. Unlike the algorithm of Gauss, this hasn't exceptions and it runs for the Gregorian Calendar, starting from 1583. The limits of the dates are march 22 and april 25. The dates of Easter have a cycle of 5,700,000 years. The most frequently date is april 19. Example for 2019: A=5, B=20, C=19, D=5, E=0, F=1, G=6, H=29, J=4, K=3, L=1, M=0, N=4, P=20 N=4 that is april, P+1=21 The Orthodox Easter follows the Julian Calendar, the algorithm is: The cycle of the dates of the Julian Easter is 532 years. Example for 2019: A=3, B=3, C=5, D=20, E=4, F=4, G=14 N=4 april, G+1=15, in the Gregorian Calendar 15+13=28 ciao Fabio Il 21/03/2019 15:35, Frank King ha scritto: Dear Roger, I note that you say: My reference on this topic is The Sun in the Church by J L Heilbron. He is pretty sound on this and, as early as page 3, notes that the time of the equinox and the time of full moon depend where you are on the planet. He adds, "as, of course does Sunday". If everyone used the Julian Date then they might all agree on the instant of the equinox and the instant of full moon but it seems most unlikely that they would have similar agreement as to what is meant by "Sunday". It takes 48 hours from the start of a given Sunday, just to the west of the International Date Line, to the end of the same Sunday, just to the east of the Line. Fabio has pointed out that Rome and Jerusalem have been suggested as candidate places for defining a Canonical Sunday. I too have read this but I don't know where the supposed primary source is. I think Fabio's explanation is the most plausible. In essence, you define an algorithm (albeit one that is a bit suspect) and impose a kind of ANSI Standard Easter :-) As a former colleague once told me: "The great thing about having Standards is that there are so many of them." You are one of the most-westerly subscribers to this list so I think a Bailey-Standard Easter would be worth lobbying for. You might thereby become a noted Holy Man. Be careful! Very best wishes Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial -- Fabio Savian fabio.sav...@nonvedolora.it www.nonvedolora.eu Paderno Dugnano, Milano, Italy 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Dear Roger, I note that you say: > My reference on this topic is The Sun in > the Church by J L Heilbron. He is pretty sound on this and, as early as page 3, notes that the time of the equinox and the time of full moon depend where you are on the planet. He adds, "as, of course does Sunday". If everyone used the Julian Date then they might all agree on the instant of the equinox and the instant of full moon but it seems most unlikely that they would have similar agreement as to what is meant by "Sunday". It takes 48 hours from the start of a given Sunday, just to the west of the International Date Line, to the end of the same Sunday, just to the east of the Line. Fabio has pointed out that Rome and Jerusalem have been suggested as candidate places for defining a Canonical Sunday. I too have read this but I don't know where the supposed primary source is. I think Fabio's explanation is the most plausible. In essence, you define an algorithm (albeit one that is a bit suspect) and impose a kind of ANSI Standard Easter :-) As a former colleague once told me: "The great thing about having Standards is that there are so many of them." You are one of the most-westerly subscribers to this list so I think a Bailey-Standard Easter would be worth lobbying for. You might thereby become a noted Holy Man. Be careful! Very best wishes Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Yes, as was mentioned, I too have heard that, for determining Easter, they use March 21 as the equinox date. As for Passover, what I heard was that that used to be part of the Easter calculation, but was dropped by the Catholic Church. ...but that the Eastern Orthodox Church still uses Passover when reckoning Easter. Michael Ossipoff On Wed, Mar 20, 2019 at 12:00 AM Roger wrote: > I always thought Easter Sunday was on the first Sunday after the first > full moon after the spring equinox. This year at my location, time zone > PDST, the equinox is at 2:59 pm Wed 20 March 2019. The full moon is about 4 > hours later at 6:43 pm. Why is this Sunday not Easter and Friday not Good > Friday. What about the Passover. It is also a month later. I know setting > the date of Easter was the problem that inspired astronomy but this year > the scientific data and the religious credo do not seem to agree. > > > > Where have I been mislead? (other than finding silly girls posing as > sundials) > > > > Roger Bailey > > Walking Shadow Designs > > N 48.669°, W 123.403° > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: Equinox, Full Moon and Easter
I would like to thank all that responded to my simple question. My intent was to use the Socratic method of “asking and answering questions to stimulate critical thinking and to draw out ideas and underlying presuppositions.” I learned long ago not to ask a question unless I knew the answer. My hypothesis is there is a human need to celebrate the joy of the coming of spring, a natural time of rebirth and growth due to longer days and more direct sunlight. As usual this natural need was co-opted, codified and enforced by religious and civil authorities. Now we have better methods based on better data from precise observations with better mathematics and astronomical science. Who do you believe. The codification by civil and religious authorities is necessary for defining Easter Sunday, Good Friday, the Passover etc. Science does a better job defining the equinox, the solstices and the seasons My reference on this topic is “Sun in the Church” by J L Heilbron. Regards, Roger Bailey From: Roger Sent: March 19, 2019 9:00 PM To: sundial@uni-koeln.de Subject: Equinox, Full Moon and Easter I always thought Easter Sunday was on the first Sunday after the first full moon after the spring equinox. This year at my location, time zone PDST, the equinox is at 2:59 pm Wed 20 March 2019. The full moon is about 4 hours later at 6:43 pm. Why is this Sunday not Easter and Friday not Good Friday. What about the Passover. It is also a month later. I know setting the date of Easter was the problem that inspired astronomy but this year the scientific data and the religious credo do not seem to agree. Where have I been mislead? Roger Bailey Walking Shadow Designs N 48.669°, W 123.403° --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
dear Roger, The computation of Easter is a little bit complex, it follows some canonical rules. There is an astronomical equinox but the canonical equinox is always the march 21. I have notice from the ephemeris that this year the astronomic full moon is on the march 21 (1:43 UT), that is in the same date of the canonical equinox. Someone says that it should be calculate in Rome, others in Jerusalem, anyway it is wrong because the reference is the canonical full moon and it is calculated with the epact, that is the moon's age at January 1. Clavius worked on calendar reform and he wrote the epact for 4000 years. This year the epact is 24. This means I have to come back 24 days to find a canonical new moon, that is december 8. Now I have calculate the spring new moon adding 30, 29, 30, 29 days. This rule needed to approximate the lunar cycle of about 29 and half. Adding 30 + 29 + 30 days I get march 7, than I have to add 13 days to get the canonical full moon and I get march 20, that is one day before the canonical equinox. For this reason the rule adds other 29 days reaching april 18, so Easter is on april 21. To get the full moon from the new moon the rule adds 13 days and not 14.76 because it starts from the observation of the first lunar sickle, that is about 30 hours later the astronomical new moon. These are the canonical rules and they differ from the astronomical abservations because the aim was to avoid complex and contestable observations, keeping the approximation as small as possible. Sometimes the rules create curious arrangement like this year: the canonical full moon of march is one day before the canonical equinox while the astronomical full moon is one day after the astronomical equinox. There also are ecceptions, for example if the canonical full moon is on april 21 and it is saturday, Easter is not on sunday 22 but on sunday 29. Someone says because in the first case the Catholic Easter overlap Passoverr but the reason is to avoid to celebrate the resurrection in the same days of the death of Christ (Coyne, G. V., Michael A. Hoskin, and O. Pedersen. Gregorian Reform of the Calendar Proceedings of the Vatican Conference to Commemorate its 400th Anniversary, 1582-1982, 1983). These infos come from the book of Piero Tempesti, Il calendario e l'orologio (the calendar and the timepiece), 2006. Tempesti deeply analyze this matter and I have summarized what Bepi De Donà recently exposed on the italian mailing-list of gnomonics about this topic. ciao Fabio Il 20/03/2019 05:00, Roger ha scritto: I always thought Easter Sunday was on the first Sunday after the first full moon after the spring equinox. This year at my location, time zone PDST, the equinox is at 2:59 pm Wed 20 March 2019. The full moon is about 4 hours later at 6:43 pm. Why is this Sunday not Easter and Friday not Good Friday. What about the Passover. It is also a month later. I know setting the date of Easter was the problem that inspired astronomy but this year the scientific data and the religious credo do not seem to agree. Where have I been mislead? (other than finding silly girls posing as sundials) Roger Bailey Walking Shadow Designs N 48.669°, W 123.403° --- https://lists.uni-koeln.de/mailman/listinfo/sundial -- Fabio Savian fabio.sav...@nonvedolora.it www.nonvedolora.eu Paderno Dugnano, Milano, Italy 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Roger, https://www.scientificamerican.com/article/how-the-moon-affects-the-date- of-easter/ This article seems to cover your point. Mike In message , Roger writes I always thought Easter Sunday was on the first Sunday after the first full moon after the spring equinox. This year at my location, time zone PDST, the equinox is at 2:59 pm Wed 20 March 2019. The full moon is about 4 hours later at 6:43 pm. Why is this Sunday not Easter and Friday not Good Friday. What about the Passover. It is also a month later. I know setting the date of Easter was the problem that inspired astronomy but this year the scientific data and the religious credo do not seem to agree. Where have I been mislead? (other than finding silly girls posing as sundials) Roger Bailey Walking Shadow Designs N 48.669°, W 123.403° --- https://lists.uni-koeln.de/mailman/listinfo/sundial -- Mike Isaacs --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinox, Full Moon and Easter
Roger, the Easter calculation uses March 21 as the equinox irrespective of the astronomy. Steve On Tue, Mar 19, 2019 at 21:00, Roger wrote: > I always thought Easter Sunday was on the first Sunday after the first > full moon after the spring equinox. This year at my location, time zone > PDST, the equinox is at 2:59 pm Wed 20 March 2019. The full moon is about 4 > hours later at 6:43 pm. Why is this Sunday not Easter and Friday not Good > Friday. What about the Passover. It is also a month later. I know setting > the date of Easter was the problem that inspired astronomy but this year > the scientific data and the religious credo do not seem to agree. > > > > Where have I been mislead? (other than finding silly girls posing as > sundials) > > > > Roger Bailey > > Walking Shadow Designs > > N 48.669°, W 123.403° > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- Cell +1 778 837 5771 --- https://lists.uni-koeln.de/mailman/listinfo/sundial
