I was just forward an e-mail that this coming February had four
Sundays, four Mondays, four Tuesdays, four Wednesday, four Thursdays, four Fridays, and four Saturdays, and that it is auspicious because it happens only once in 823 years. Of course, every February has four of each date, though leap years have a 5th of one day of the week. So 303 of 400 years have exactly four of each. Doing some googling I found that February 2015 and February 2016 were also "auspicious". When someone challenged February 2015, the response was that it uses four week-rows on a Calendar (which is true at least in North America, since February 1, 2015 was a Sunday). But this happens 3 times in 28 years (ignoring 2100, 2200, 2300, 2500, etc.) There are also versions regarding 5 weekends (Friday-Sunday) in a month, which happens whenever a 31-day month begins on a Friday and ends on a Sunday of the 5th Weekend. So this should happen on average of once per year, or more precisely twice per year (years beginning on Sunday, January 1st), once per year five of seven years, and none in one of seven years. Since this is supposedly based on Chinese astrology, it is unlikely to be based on the Gregorian calendar. So I was wondering, how are months calculated in a Chinese calendar. Are they all 29 or 30 days, or is there a rare 28-day month based on a mathematical formula, rather than an actual observation? Alternately is there some relationship between the tropical month, the synodic month, and the anomalistic month? If I'm thinking right, the shortest synodic months (new moon to new moon) are when the full moon is near apogee, so that the extra angular distance the moon must travel (about 389 degrees?) is done around the perigee just after the new moon at the start of the month and the perigee just before the new moon at the end of the month. But what if we take into account the anomalistic month (perigee to perigee) and tropical month, so it would be coincident with the year? Is that a period of 823 years? It is possible that 823 is the "whopper" answer in the game of "truth, fibs, and whoppers" -- Jim Riley |
Hi Jim and calendar people, Since the Gregorian calendar has a 400-year cycle, no calendar phenomenon can occur once every 823 years. |
Dear Amos and Calendar People
I find that 823 years has about 303.08 leap months and so could be a lunisolar cycle. 45 Metonic cycles have 855 years, subtract 4 octaeterides from this an one gets 823 years. However the 823 years may just be made up to put some "alternative facts" onto the internet. Also I calculated that the months with five Fridays, Saturdays & Sundays occur exactly once a year on average in the Gregorian Calendar as well as the Julian Calendar. Karl 16(06(01 till noon ________________________________ From: East Carolina University Calendar discussion List [[hidden email]] on behalf of Amos Shapir [[hidden email]] Sent: 29 January 2017 08:02 To: [hidden email] Subject: Re: 823-year cycle Hi Jim and calendar people, Since the Gregorian calendar has a 400-year cycle, no calendar phenomenon can occur once every 823 years. This number suggests that the original message had some other calendar in mind, possibly a lunar or luni-solar one. |
The 823-year cycle is well known on the Internet (google for "823 year
myth"). Moreover, the four or each day of the week in February has spread every February since at least 2010. The version forwarded to me read: > This won't come in our lifetime again. > > This February has 4 Sundays, 4 Mondays, 4 Tuesdays, 4 Wednesdays, > 4 Thursdays, 4 Fridays & 4 Saturdays. > > This only happens once every 823 years. So the Year has been stripped, and something that happens every February (or perhaps 303 out of 400 February's) has been made to seem exotic by inclusion of a long cycle of years that happens to be prime. It is trivial to de-hoax, and has even resulted in cartoons to do so. https://www.youtube.com/watch?v=4Mx4shB37yM But is there somehow a kernel of truth? That there are five weekends in some months is at least interesting, but someone noting that February had four of each day of the week might be mocking them. A more formal version claims that a relationship to Feng Shui money bags. An interesting de-hoaxing noted that if it was 823 years between this auspicious event, how was it known, and suggested that instead of chain letters, they were exchanging chain stone tablets). These two, particularly the second suggest a connection between day of year, day of week, and lunar phase. The claim that someone remembered a letter to the editor from The Telegraph from 1972 is somewhat dubious, but there are surely persons more eccentric than even the subscribers to this list. February 29, 1972 was indeed a Tuesday and a full moon. https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Mathematics/2015_February_10 https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Mathematics/2015_February_17#Is_it_an_anomaly_that_the_month_of_February_2015_contains_four_occurrences_of_each_day_of_the_week.3F_.28February_10.29 Because I received the email the day before Chinese New Year, and the association with Feng Shui, I speculated that there was a connection to the Chinese Calendar. I think I read that the months in the calendar are independent of the year (perhaps running in a 60-month cycle) like the years, and that a different calendar is used for applications such as planting. Could there be some coincidence between an auspicious year, and auspicious month, and the New Year? On Sun, 29 Jan 2017 09:21:41 +0000, Karl Palmen <[hidden email]> wrote: >Dear Amos and Calendar People > >I find that 823 years has about 303.08 leap months and so could be a lunisolar cycle. >45 Metonic cycles have 855 years, subtract 4 octaeterides from this an one gets 823 years. > >However the 823 years may just be made up to put some "alternative facts" onto the internet. > >Also I calculated that the months with five Fridays, Saturdays & Sundays occur exactly once a year on average in the Gregorian Calendar as well as the Julian Calendar. In my response to the original message claiming that February 2017 was a once in 823 year event, I had noted the 5 weekends phenomena and explained how it worked for months with 31 days. I then went on to ask: > Trick question. As you know, months alternate in length. How many of > the twelve months have 31 days. > > Generational question. How did you figure out the answer: > (0) Divided 12 by two. > (1) Used my knuckles. > (2) Remembered the nursery rhyme, "30 days hath September ..." > (3) Checked my wall calendar. > (4) Pulled up my calendar app. -- Jim Riley |
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