bug#36918: 26.2.90; calendar: the chinese sexagesimal name for month is wrong

bug#36918: 26.2.90; calendar: the chinese sexagesimal name for month is wrong

[Zhang Haijun]

In GNU Emacs 26.2.90 (build 1, x86_64-apple-darwin17.7.0, NS appkit-1561.60 Version 10.13.6 (Build 17G7024))
 of 2019-06-15 built on jundeMac
Windowing system distributor 'Apple', version 10.3.1561
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Computing Chinese date...
Chinese date: Cycle 78, year 36 (Ji-Hai), month 7 (Ren-Shen), day 4 (Gui-You)

———————————————————————

The sexagesimal name for month today should be Xin-Wei not Ren-Shen. It will becomes Ren-Shen after 4 days(on 8/8. which is the beginning of autumn). As far as I known, It always changes at the monment when the ecliptic longitude is 15, 45, 75 … (for every 30 degrees).


Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
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 Support/Emacs/site-lisp' --with-modules --disable-acl
 --without-makeinfo 'CC=cc ' CFLAGS=-O2
 PKG_CONFIG_PATH=/Users/jun/source/build-emacs-master/brew/lib/pkgconfig:'

Configured features:
JPEG NOTIFY GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES THREADS
LCMS2

Important settings:
  value of $LANG: zh_CN.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

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Memory information:
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bug#36918: Acknowledgement (26.2.90; calendar: the chinese sexagesimal name for month is wrong)

[Zhang Haijun]

Reproduction steps:
1. emacs -Q
2. M-x calendar
3. p C
4. It will print the chinese date at the echo area.

The sexagesimal name for month today(4/8/2019) should be Xin-Wei not Ren-Shen. It will becomes Ren-Shen on 8/8/2019.

bug#36918: 26.2.90; calendar: the chinese sexagesimal name for month is wrong

[Basil L. Contovounesios]

Zhang Haijun <ccsmile2008@outlook.com> writes:

> The sexagesimal name for month today should be Xin-Wei not
> Ren-Shen. It will becomes Ren-Shen after 4 days(on 8/8. which is the
> beginning of autumn). As far as I known, It always changes at the
> monment when the ecliptic longitude is 15, 45, 75 … (for every 30
> degrees).

Sorry, I am not very familiar with either the Chinese calendar or the
Calendar app, but I think the following points might be of interest.

The cal-china.el package contains the following disclaimer in its
commentary:

  The rules used for the Chinese calendar are those of Baolin Liu
  (see L. E. Doggett's article "Calendars" in the Explanatory
  Supplement to the Astronomical Almanac, second edition, 1992) for
  the calendar as revised at the beginning of the Qing dynasty in
  1644.  The nature of the astronomical calculations is such that
  precise calculations cannot be made without great expense in time,
  so that the calendars produced may not agree perfectly with
  published tables--but no two pairs of published tables agree
  perfectly either!  Liu's rules produce a calendar for 2033 which is
  not accepted by all authorities.  The date of Chinese New Year is
  correct from 1644-2051.

p C (calendar-chinese-print-date) describes 2019-08-05 as follows:

  Cycle 78, year 36 (Ji-Hai), month 7 (Ren-Shen), day 5 (Jia-Xu)

and a quick online search revealed two websites[1][2] which give a
similar description:

  Ji Hai Year (4717), Ren Shen Month (7), Jia Xu Day (5)

[1]: https://www.travelchinaguide.com/intro/focus/calendar.htm
[2]: https://www.prokerala.com/general/calendar/chinese-year-converter.php

So to an ignorant person like me, there is nothing obviously wrong with
Emacs' calculations.  Perhaps someone else can shine some more light on
this.

Thanks,

-- 
Basil

bug#36918: 26.2.90; calendar: the chinese sexagesimal name for month is wrong

[Zhang Haijun]

> p C (calendar-chinese-print-date) describes 2019-08-05 as follows:
> 
>  Cycle 78, year 36 (Ji-Hai), month 7 (Ren-Shen), day 5 (Jia-Xu)
> 
> and a quick online search revealed two websites[1][2] which give a
> similar description:
> 
>  Ji Hai Year (4717), Ren Shen Month (7), Jia Xu Day (5)
> 
> [1]: https://www.travelchinaguide.com/intro/focus/calendar.htm

At the tail of the article in this page(https://www.travelchinaguide.com/intro/astrology/60year-cycle.htm), it says:

 * The Gregorian year is approximate here. The accurate division is the Beginning of Spring (first of the 24 Solar Terms), although some online calendars adopt Chinese New Year as the division.

It mentions two division methods. The former is right (at the moment the ecliptic longitude is 315°). It differs too much with the latter(the first day of the first month), maybe saveral days like in this month(8 days).


> [2]: https://www.prokerala.com/general/calendar/chinese-year-converter.php
> 

The result in this page shows the month is Xin-Wei which is right:

https://www.prokerala.com/general/calendar/chinesecalendar.php


There are two seperated systems (or two calendars) in Chinese calendar. One of them is the 60-Year Cycle, which is the topic of this thread. It is standalone with the rest of Chinese calendar. It is a solar calendar. It is fully based on the 24 Solar Terms and has no relation with the rest of Chinese calendar. It is not commonly used. It is mainly used for scrying.