Re:
> > On 23 Mar 2019, at 15:51, Michael Ossipoff wrote: > > > > > The International Standards Organization WeekDate calendar (ISO > > WeekDate > > Calendar): > > > > . > > > > The calendar year starts with the Monday closest to Gregorian January > > 1st. > > > > Close. No, not just close. My definition is a correct wording for a definition of ISO WeekDate. > The start of each week is defined as a Monday. The first week of > the year is the first week of the calendar year that contains a > Thursday. > > Effectively, the same thing as you describe, but the definition makes no > reference to Monday or January 1st. > You mean that the definition *that you read* makes no reference to Monday or to January 1st. I didn't say that I was quoting the official wording, or the Wikipedia wording. I was giving a less arbitrary-sounding, clearly, naturally and obviously-motivated wording of the definition. In other words, a better wording of the definition. Michael Ossipoff 13 Sa 1958 UTC > Barry > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
[no subject]
Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die eigentliche Nachricht steht dadurch in einem Anhang. This message was wrapped to be DMARC compliant. The actual message text is therefore in an attachment.--- Begin Message --- On 23 Mar 2019, at 15:51, Michael Ossipoff wrote: The International Standards Organization WeekDate calendar (ISO WeekDate Calendar): . The calendar year starts with the Monday closest to Gregorian January 1st. Close. The start of each week is defined as a Monday. The first week of the year is the first week of the calendar year that contains a Thursday. Effectively, the same thing as you describe, but the definition makes no reference to Monday or January 1st. Barry --- End Message --- --- https://lists.uni-koeln.de/mailman/listinfo/sundial
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
