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RFC for help with Julian calendar conversion algorithm
There's a somewhat technical mathematical discussion at the Julian day article related to how algorithms convert Julian date to calendar date. I think some of the people watching this article might be able to contribute. Here's the specific RFC section: Talk:Julian_day#Request_For_Comment_on_presentation_of_algorithms— Preceding unsigned comment added by Timtempleton (talk • contribs) 22:58, 27 November 2017 (UTC)
Semi-protected edit request on 18 June 2022
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- Comment: makes sense, given that the relevant article is Hijrah not Hegira. --John Maynard Friedman (talk) 12:56, 18 June 2022 (UTC)
Semi-inaccuracy in top section
The number 365.2422 is the current length of the "mean tropical year", but the Gregorian calendar reformers weren't trying to approximate that (I'm not sure that the concept of mean tropical year was known in 1582). Since one of the main motivations of the Gregorian reform was to correct the date of Easter, and Easter is defined in terms of the vernal equinox, they were trying to approximate the vernal equinox year, or time interval separating vernal equinoxes, which is not exactly the same (the equinox interval is mentioned prominently near the beginning of our tropical year article). According to Tropical year#Different tropical year definitions, the current length of the vernal equinox year is 365.242374 days, and this number is more relevant for judging the accuracy of the Gregorian calendar than 365.2422. The devisers of the Revised Julian Calendar ignored this when they made the average year length be 365.242 days (a disimprovement with respect to the vernal equinox year -- they were more desperate to show their independence from Catholics by having their calendar not be exactly the same, than thinking about the historical function of the calendar with respect to Christianity). AnonMoos (talk) 09:49, 14 October 2022 (UTC)
:Time for a WP:rs then. How accurately could astronomers of the day measure the tropical year? And the reformers had to consider what would be acceptable and explicable to a substantially illiterate and inumerate "flock". The algorithm is good enough. IMO, the current statement in the lead is also good enough for our purposes: the "perfect" is described in detail in the body. We know that the orbit of planet earth is not a perfect metronome, so approximations will always be needed. For almost all of the people for almost all of the time, the niceties are entirely background radiation. --𝕁𝕄𝔽 (talk) 10:14, 14 October 2022 (UTC)
- Reading on mobile, I see I didn't quite appreciate your question, my apologies. Would it meet your objection if the current
more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun.were rephrased as
more closely approximating the true duration of the time between vernal equinoxes, which is a little less than than the 365.25 days in the Julian calendar.I think we can say that without breaking WP:OR (and the present lead doesn't even say what the Julian figure is, so needs adding).
- BTW, we shouldn't really say determined by the Earth's revolution around the Sun. since at the time the sun went around the earth. --𝕁𝕄𝔽 (talk) 17:10, 14 October 2022 (UTC)
Where angels fear to tread
I decided to be bold and give effect to this discussion so that the lead would read
The Gregorian calendar is the calendar used in most parts of the world.ref It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, which is a little less than than the 365.25 days in the Julian calendar but which more closely approximates the true duration of the time between vernal equinoxes.
but that introduces duplication in close succession, because the next para (after stating the rule) reads
There were two reasons to establish the Gregorian calendar. First, the Julian calendar assumed incorrectly that the average solar year is exactly 365.25 days long, an overestimate of a little under one day per century, and thus has a leap year every four years without exception. The Gregorian reform shortened the average (calendar) year by 0.0075 days to stop the drift of the calendar with respect to the equinoxes.
Would it be too terse to delete
There were two reasons to establish the Gregorian calendar. First, the Julian calendar assumed incorrectly that the average solar year is exactly 365.25 days long, an overestimate of a little under one day per century, and thus has a leap year every four years without exception. ? --𝕁𝕄𝔽 (talk) 13:26, 18 October 2022 (UTC)
- No, not delete. How about
There were two reasons to establish the Gregorian calendar. First, the Julian calendar overestimated the length of the year by a little under one day per century, and thus has a leap year every four years without exception.Better? --𝕁𝕄𝔽 (talk) 15:06, 18 October 2022 (UTC)
Swapping description and lead sections?
Would it be better to move a bunch of the stuff in "Description" into the lead section, and move what's now in the lead section to a "History" section? The lead section right now really assumes you already are very familiar with the Gregorian calendar, which reads a bit odd to me. AapeliV (talk) 00:32, 1 January 2023 (UTC)
Semi-protected edit request on 4 February 2023
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Please remove this sentence:
Because the date of Easter is a function – the computus – of the date of the (northern hemisphere) spring equinox
and add this one:
Because the date of Easter is a function – the computus – of the date of the spring equinox in the northern hemisphere