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Talk:Gregorian calendar

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North Korean Calendar?

In the infobox there is no reference to the North Korean Calendar[1]. PLEASE ADD! 120.151.205.179 (talk) 10:13, 18 August 2015 (UTC)

Yes, it is, under "Juche calendar". --John Maynard Friedman (talk) 19:30, 17 December 2016 (UTC)

References

Inter Gravissimas (W. Spenser & R. T. Crowley, Trans.) paywalled. Is there an open source of this translation?

This is paywalled:

Is there another source for this translation of Inter Gravissimas?

--Geremia (talk) 20:41, 21 March 2016 (UTC)

Astronomers are subject to WP:RS and WP:V the same as anybody else

thread started by banned user. Fut.Perf. 18:29, 5 April 2016 (UTC)
The following discussion has been closed. Please do not modify it.

Jc3s5h has added a claim which, apart from making the nonsense statement that the vernal equinox is a certain number of days apart cites a source which gives the alleged separation to six places of decimals. This is unverifiable. It is said to relate to "near 2000" but a check cannot be made because how near is not specified. In some contexts 1900 might be "near 2000", in others 1995 might be rather far away. 77.98.244.158 (talk) 22:57, 28 March 2016 (UTC)

Are you claiming that Meeus and Savoie (1992), p. 42 is not a reliable source? Dbfirs 19:46, 4 April 2016 (UTC)
It's a question of verification. You've conspicuously failed to verify those six - figure decimal values. 77.98.244.158 (talk) 20:26, 4 April 2016 (UTC)
I don't need to personally verify them, just to cite them from a WP:reliable source. "Jean Meeus explores the frequency of blue moons, planetary groupings, and a great deal more, as only this master of astronomical calculations could." Dbfirs 20:42, 4 April 2016 (UTC)
What a joke. What have blue moons and planetary alignments have to do with the theory behind the calendar? 77.98.244.158 (talk) 20:53, 4 April 2016 (UTC)
Read the second half of the cite. Dbfirs 07:09, 5 April 2016 (UTC)
The cite contains 23 words. So the second half of it is "a great deal more, as only this master of astronomical calculations could". Are you Jan Meeus' PR agent? How does that verify a time - dependent algorithm, for which no time argument is given, to six places of decimals? At 15:07, 10 May 2015 you said

The values for the equinox and solstice years were presumably calculated by the same method, but using the true longitude instead of the mean longitude.

I get the distinct impression that you don't have the faintest idea what you are talking about. 77.98.244.158 (talk) 12:23, 5 April 2016 (UTC)

I agree that neither of us has been able to find the methodology used by Jean Meeus (of whom I had never heard until you objected to his research), but his figures seem to be a modification of the formula derived by Jacques Laskar for the mean tropical year, or of one of the more recent equivalents. He gives a time argument (J2000) for the figure cited. Dbfirs 13:05, 5 April 2016 (UTC)

Mean Solar Days

The current value of the tropical year is about 365.242181 mean solar days (please note that these are slightly different from ephemeris days). By my calculation, this makes the Gregorian calendar accurate to one day in about 3135 years. Have I miscalculated, or are other people comparing apples with pears? The estimation is slightly suspect, of course, because the length of the mean solar day changes slightly over time, but I don't see how the figure in the article is arrived at unless someone is using inappropriate rounding. Dbfirs 07:45, 6 October 2016 (UTC)

I found that the value in the article, 1 day per 3327 years was substantially introduced in this 2005 edit by an editor who does not appear to be active. It was changed from 3300 years to 3327 years by an IP editor recently. I cannot reproduce this value.
I also cannot reproduce Dbfirs' value of 365.242181 mean solar days for the tropical year. Richards (p. 587) gives a value of 365.24217 mean solar days per year, or 365.24219 days if the day is 86,400 SI seconds. This is for 2000, but the formula on page 586 shows the change from 2000 to 2016 is negligible. When I use the value of 365.24217 mean solar days per year, and divide by the tropical year when calculating the error, I get an error of 1 day per 3030 years. Jc3s5h (talk) 13:55, 6 October 2016 (UTC)

References

Richards, E. G. (2013) "Calendars" in S. E. Urban and P. K. Seidelmann Explanatory Supplement to the Astronomical Almanac (3rd ed.). Mill Valley CA: University Science Books. ISBN 978-1-891389-85-0

I must admit that I copied the value from the lead in our article Tropical year and not from an academic reference. Perhaps this article needs changing? Using Richards' value, I agree with your 3030 years. Would you like to make the appropriate changes? Dbfirs 07:30, 7 October 2016 (UTC)
OK. I'll have a look at "Tropical year too. Good catches. Jc3s5h (talk) 13:45, 7 October 2016 (UTC)
Thank you for updating the values. Dbfirs 15:56, 7 October 2016 (UTC)

Semi-protected edit request on 21 December 2016

In the table 'Adoption of Gregorian Calendar', please add Poland/Lithuania. Below part of the code changed to corrected form. Source? Wikipedia in the same paragraph, a few lines above the table. Astymo (talk) 23:06, 21 December 2016 (UTC)

Thank you for your contribution. Unfortunately the text a few lines up is unsourced, so I've tagged it and thus your reasonable request will have to wait until evidence is produced. [By the way, one of our fundamental principles is that Wikipedia must never cite itself. That way madness lies. --John Maynard Friedman (talk) 00:41, 22 December 2016 (UTC)

Ok. Understood. So please see below few links to confirm information about Adoption of Gregorian calendar in Poland-Lithuania, as one of the first states. I hope it will be enough. http://www.webexhibits.org/calendars/year-countries.html https://www.timeanddate.com/calendar/julian-gregorian-switch.html http://www.messagetoeagle.com/the-gregorian-calendar-implemented-on-oct-5-1582/ http://www.almanac.com/fact/first-day-of-conversion-to-gregorian-calendar — Preceding unsigned comment added by Astymo (talkcontribs) 21:07, 3 February 2017 (UTC)

Done Stickee (talk) 00:13, 2 March 2017 (UTC)

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