1 ;;; cal-china.el --- calendar functions for the Chinese calendar.
3 ;; Copyright (C) 1995, 1997 Free Software Foundation, Inc.
5 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Human-Keywords: Chinese calendar, calendar, holidays, diary
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation; either version 2, or (at your option)
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs; see the file COPYING. If not, write to the
23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
24 ;; Boston, MA 02111-1307, USA.
28 ;; This collection of functions implements the features of calendar.el,
29 ;; diary.el, and holidays.el that deal with the Chinese calendar. The rules
30 ;; used for the Chinese calendar are those of Baolin Liu (see L. E. Doggett's
31 ;; article "Calendars" in the Explanatory Supplement to the Astronomical
32 ;; Almanac, second edition, 1992) for the calendar as revised at the beginning
33 ;; of the Qing dynasty in 1644. The nature of the astronomical calculations
34 ;; is such that precise calculations cannot be made without great expense in
35 ;; time, so that the calendars produced may not agree perfectly with published
36 ;; tables--but no two pairs of published tables agree perfectly either! Liu's
37 ;; rules produce a calendar for 2033 which is not accepted by all authorities.
38 ;; The date of Chinese New Year is correct from 1644-2051.
40 ;; Technical details of all the calendrical calculations can be found in
41 ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
42 ;; Cambridge University Press (1997).
44 ;; Comments, corrections, and improvements should be sent to
45 ;; Edward M. Reingold Department of Computer Science
46 ;; (217) 333-6733 University of Illinois at Urbana-Champaign
47 ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
48 ;; Urbana, Illinois 61801
54 (defvar chinese-calendar-celestial-stem
55 ["Jia" "Yi" "Bing" "Ding" "Wu" "Ji" "Geng" "Xin" "Ren" "Gui"])
57 (defvar chinese-calendar-terrestrial-branch
58 ["Zi" "Chou" "Yin" "Mao" "Chen" "Si" "Wu" "Wei" "Shen" "You" "Xu" "Hai"])
60 (defcustom chinese-calendar-time-zone
64 "*Number of minutes difference between local standard time for Chinese
65 calendar and Coordinated Universal (Greenwich) Time. Default is for Beijing.
66 This is an expression in `year' since it changed at 1928-01-01 00:00:00 from
69 :group
'chinese-calendar
)
71 (defcustom chinese-calendar-location-name
"Beijing"
72 "*Name of location used for calculation of Chinese calendar."
74 :group
'chinese-calendar
)
76 (defcustom chinese-calendar-daylight-time-offset
0
77 ; The correct value is as follows, but the Chinese calendrical
78 ; authorities do NOT use DST in determining astronomical events:
80 "*Number of minutes difference between daylight savings and standard time
81 for Chinese calendar. Default is for no daylight savings time."
83 :group
'chinese-calendar
)
85 (defcustom chinese-calendar-standard-time-zone-name
89 "*Abbreviated name of standard time zone used for Chinese calendar.
90 This is an expression depending on `year' because it changed
91 at 1928-01-01 00:00:00 from `PMT' to `CST'."
93 :group
'chinese-calendar
)
95 (defcustom chinese-calendar-daylight-time-zone-name
"CDT"
96 "*Abbreviated name of daylight-savings time zone used for Chinese calendar."
98 :group
'chinese-calendar
)
100 (defcustom chinese-calendar-daylight-savings-starts nil
101 ; The correct value is as follows, but the Chinese calendrical
102 ; authorities do NOT use DST in determining astronomical events:
103 ; '(cond ((< 1986 year) (calendar-nth-named-day 1 0 4 year 10))
104 ; ((= 1986 year) '(5 4 1986))
106 "*Sexp giving the date on which daylight savings time starts for Chinese
107 calendar. Default is for no daylight savings time. See documentation of
108 `calendar-daylight-savings-starts'."
110 :group
'chinese-calendar
)
112 (defcustom chinese-calendar-daylight-savings-ends nil
113 ; The correct value is as follows, but the Chinese calendrical
114 ; authorities do NOT use DST in determining astronomical events:
115 ; '(if (<= 1986 year) (calendar-nth-named-day 1 0 9 year 11))
116 "*Sexp giving the date on which daylight savings time ends for Chinese
117 calendar. Default is for no daylight savings time. See documentation of
118 `calendar-daylight-savings-ends'."
120 :group
'chinese-calendar
)
122 (defcustom chinese-calendar-daylight-savings-starts-time
0
123 "*Number of minutes after midnight that daylight savings time starts for
124 Chinese calendar. Default is for no daylight savings time."
126 :group
'chinese-calendar
)
128 (defcustom chinese-calendar-daylight-savings-ends-time
0
129 "*Number of minutes after midnight that daylight savings time ends for
130 Chinese calendar. Default is for no daylight savings time."
132 :group
'chinese-calendar
)
134 (defun chinese-zodiac-sign-on-or-after (d)
135 "Absolute date of first new Zodiac sign on or after absolute date d.
136 The Zodiac signs begin when the sun's longitude is a multiple of 30 degrees."
137 (let* ((year (extract-calendar-year
138 (calendar-gregorian-from-absolute d
)))
139 (calendar-time-zone (eval chinese-calendar-time-zone
))
140 (calendar-daylight-time-offset
141 chinese-calendar-daylight-time-offset
)
142 (calendar-standard-time-zone-name
143 chinese-calendar-standard-time-zone-name
)
144 (calendar-daylight-time-zone-name
145 chinese-calendar-daylight-time-zone-name
)
146 (calendar-calendar-daylight-savings-starts
147 chinese-calendar-daylight-savings-starts
)
148 (calendar-daylight-savings-ends
149 chinese-calendar-daylight-savings-ends
)
150 (calendar-daylight-savings-starts-time
151 chinese-calendar-daylight-savings-starts-time
)
152 (calendar-daylight-savings-ends-time
153 chinese-calendar-daylight-savings-ends-time
))
155 (calendar-absolute-from-astro
156 (solar-date-next-longitude
157 (calendar-astro-from-absolute d
)
160 (defun chinese-new-moon-on-or-after (d)
161 "Absolute date of first new moon on or after absolute date d."
162 (let* ((year (extract-calendar-year
163 (calendar-gregorian-from-absolute d
)))
164 (calendar-time-zone (eval chinese-calendar-time-zone
))
165 (calendar-daylight-time-offset
166 chinese-calendar-daylight-time-offset
)
167 (calendar-standard-time-zone-name
168 chinese-calendar-standard-time-zone-name
)
169 (calendar-daylight-time-zone-name
170 chinese-calendar-daylight-time-zone-name
)
171 (calendar-calendar-daylight-savings-starts
172 chinese-calendar-daylight-savings-starts
)
173 (calendar-daylight-savings-ends
174 chinese-calendar-daylight-savings-ends
)
175 (calendar-daylight-savings-starts-time
176 chinese-calendar-daylight-savings-starts-time
)
177 (calendar-daylight-savings-ends-time
178 chinese-calendar-daylight-savings-ends-time
))
180 (calendar-absolute-from-astro
181 (lunar-new-moon-on-or-after
182 (calendar-astro-from-absolute d
))))))
184 (defvar chinese-year-cache
185 '((1989 (12 726110) (1 726139) (2 726169) (3 726198) (4 726227) (5 726257)
186 (6 726286) (7 726316) (8 726345) (9 726375) (10 726404) (11 726434))
187 (1990 (12 726464) (1 726494) (2 726523) (3 726553) (4 726582) (5 726611)
188 (5.5
726641) (6 726670) (7 726699) (8 726729) (9 726758) (10 726788)
190 (1991 (12 726848) (1 726878) (2 726907) (3 726937) (4 726966) (5 726995)
191 (6 727025) (7 727054) (8 727083) (9 727113) (10 727142) (11 727172))
192 (1992 (12 727202) (1 727232) (2 727261) (3 727291) (4 727321) (5 727350)
193 (6 727379) (7 727409) (8 727438) (9 727467) (10 727497) (11 727526))
194 (1993 (12 727556) (1 727586) (2 727615) (3 727645) (3.5
727675) (4 727704)
195 (5 727734) (6 727763) (7 727793) (8 727822) (9 727851) (10 727881)
197 (1994 (12 727940) (1 727969) (2 727999) (3 728029) (4 728059) (5 728088)
198 (6 728118) (7 728147) (8 728177) (9 728206) (10 728235) (11 728265))
199 (1995 (12 728294) (1 728324) (2 728353) (3 728383) (4 728413) (5 728442)
200 (6 728472) (7 728501) (8 728531) (8.5
728561) (9 728590) (10 728619)
202 (1996 (12 728678) (1 728708) (2 728737) (3 728767) (4 728796) (5 728826)
203 (6 728856) (7 728885) (8 728915) (9 728944) (10 728974) (11 729004))
204 (1997 (12 729033) (1 729062) (2 729092) (3 729121) (4 729151) (5 729180)
205 (6 729210) (7 729239) (8 729269) (9 729299) (10 729328) (11 729358))
206 (1998 (12 729388) (1 729417) (2 729447) (3 729476) (4 729505) (5 729535)
207 (5.5
729564) (6 729593) (7 729623) (8 729653) (9 729682) (10 729712)
209 (1999 (12 729771) (1 729801) (2 729831) (3 729860) (4 729889) (5 729919)
210 (6 729948) (7 729977) (8 730007) (9 730036) (10 730066) (11 730096))
211 (2000 (12 730126) (1 730155) (2 730185) (3 730215) (4 730244) (5 730273)
212 (6 730303) (7 730332) (8 730361) (9 730391) (10 730420) (11 730450)))
213 "An assoc list of Chinese year structures as determined by `chinese-year'.
215 Values are computed as needed, but to save time, the initial value consists
216 of the precomputed years 1989-2000. The code works just as well with this
217 set to nil initially (which is how the value for 1989-2000 was computed).")
219 (defun chinese-year (y)
220 "The structure of the Chinese year for Gregorian year Y.
221 The result is a list of pairs (i d), where month i begins on absolute date d,
222 of the Chinese months from the Chinese month following the solstice in
223 Gregorian year Y-1 to the Chinese month of the solstice of Gregorian year Y.
225 The list is cached for further use."
226 (let ((list (cdr (assoc y chinese-year-cache
))))
229 (setq list
(compute-chinese-year y
))
230 (setq chinese-year-cache
231 (append chinese-year-cache
(list (cons y list
))))))
234 (defun number-chinese-months (list start
)
235 "Assign month numbers to the lunar months in LIST, starting with START.
236 Numbers are assigned sequentially, START, START+1, ..., 11, with half
237 numbers used for leap months.
239 First month of list will never be a leap month, nor will the last."
241 (if (zerop (- 12 start
(length list
)))
242 ;; List is too short for a leap month
243 (cons (list start
(car list
))
244 (number-chinese-months (cdr list
) (1+ start
)))
247 (list start
(car list
))
249 (if (and (cdr (cdr list
));; at least two more months...
250 (<= (car (cdr (cdr list
)))
251 (chinese-zodiac-sign-on-or-after (car (cdr list
)))))
252 ;; Next month is a leap month
253 (cons (list (+ start
0.5) (car (cdr list
)))
254 (number-chinese-months (cdr (cdr list
)) (1+ start
)))
255 ;; Next month is not a leap month
256 (number-chinese-months (cdr list
) (1+ start
)))))))
258 (defun chinese-month-list (start end
)
259 "List of starting dates of Chinese months from START to END."
261 (let ((new-moon (chinese-new-moon-on-or-after start
)))
262 (if (<= new-moon end
)
264 (chinese-month-list (1+ new-moon
) end
))))))
266 (defun compute-chinese-year (y)
267 "Compute the structure of the Chinese year for Gregorian year Y.
268 The result is a list of pairs (i d), where month i begins on absolute date d,
269 of the Chinese months from the Chinese month following the solstice in
270 Gregorian year Y-1 to the Chinese month of the solstice of Gregorian year Y."
271 (let* ((next-solstice (chinese-zodiac-sign-on-or-after
272 (calendar-absolute-from-gregorian
274 (list (chinese-month-list (1+ (chinese-zodiac-sign-on-or-after
275 (calendar-absolute-from-gregorian
276 (list 12 15 (1- y
)))))
278 (next-sign (chinese-zodiac-sign-on-or-after (car list
))))
279 (if (= (length list
) 12)
280 ;; No room for a leap month, just number them 12, 1, 2, ..., 11
281 (cons (list 12 (car list
))
282 (number-chinese-months (cdr list
) 1))
283 ;; Now we can assign numbers to the list for y
284 ;; The first month or two are special
285 (if (or (> (car list
) next-sign
) (>= next-sign
(car (cdr list
))))
286 ;; First month on list is a leap month, second is not
287 (append (list (list 11.5 (car list
))
288 (list 12 (car (cdr list
))))
289 (number-chinese-months (cdr (cdr list
)) 1))
290 ;; First month on list is not a leap month
291 (append (list (list 12 (car list
)))
292 (if (>= (chinese-zodiac-sign-on-or-after (car (cdr list
)))
293 (car (cdr (cdr list
))))
294 ;; Second month on list is a leap month
295 (cons (list 12.5 (car (cdr list
)))
296 (number-chinese-months (cdr (cdr list
)) 1))
297 ;; Second month on list is not a leap month
298 (number-chinese-months (cdr list
) 1)))))))
300 (defun calendar-absolute-from-chinese (date)
301 "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
302 The Gregorian date Sunday, December 31, 1 BC is imaginary."
303 (let* ((cycle (car date
))
304 (year (car (cdr date
)))
305 (month (car (cdr (cdr date
))))
306 (day (car (cdr (cdr (cdr date
)))))
307 (g-year (+ (* (1- cycle
) 60);; years in prior cycles
308 (1- year
) ;; prior years this cycle
309 -
2636))) ;; years before absolute date 0
310 (+ (1- day
);; prior days this month
312 (cdr ;; absolute date of start of this month
313 (assoc month
(append (memq (assoc 1 (chinese-year g-year
))
314 (chinese-year g-year
))
315 (chinese-year (1+ g-year
)))))))))
317 (defun calendar-chinese-from-absolute (date)
318 "Compute Chinese date (cycle year month day) corresponding to absolute DATE.
319 The absolute date is the number of days elapsed since the (imaginary)
320 Gregorian date Sunday, December 31, 1 BC."
321 (let* ((g-year (extract-calendar-year
322 (calendar-gregorian-from-absolute date
)))
323 (c-year (+ g-year
2695))
324 (list (append (chinese-year (1- g-year
))
325 (chinese-year g-year
)
326 (chinese-year (1+ g-year
)))))
327 (while (<= (car (cdr (car (cdr list
)))) date
)
328 ;; the first month on the list is in Chinese year c-year
329 ;; date is on or after start of second month on list...
330 (if (= 1 (car (car (cdr list
))))
331 ;; second month on list is a new Chinese year
332 (setq c-year
(1+ c-year
)))
333 ;; ...so first month on list is of no interest
334 (setq list
(cdr list
)))
335 (list (/ (1- c-year
) 60)
336 (calendar-mod c-year
60)
338 (1+ (- date
(car (cdr (car list
))))))))
340 (defun holiday-chinese-new-year ()
341 "Date of Chinese New Year."
342 (let ((m displayed-month
)
344 (increment-calendar-month m y
1)
346 (let ((chinese-new-year
347 (calendar-gregorian-from-absolute
348 (car (cdr (assoc 1 (chinese-year y
)))))))
349 (if (calendar-date-is-visible-p chinese-new-year
)
351 (list chinese-new-year
352 (format "Chinese New Year (%s)"
353 (calendar-chinese-sexagesimal-name (+ y
57))))))))))
355 (defun calendar-chinese-date-string (&optional date
)
356 "String of Chinese date of Gregorian DATE.
357 Defaults to today's date if DATE is not given."
358 (let* ((a-date (calendar-absolute-from-gregorian
359 (or date
(calendar-current-date))))
360 (c-date (calendar-chinese-from-absolute a-date
))
362 (year (car (cdr c-date
)))
363 (month (car (cdr (cdr c-date
))))
364 (day (car (cdr (cdr (cdr c-date
)))))
365 (this-month (calendar-absolute-from-chinese
366 (list cycle year month
1)))
367 (next-month (calendar-absolute-from-chinese
368 (list (if (= year
60) (1+ cycle
) cycle
)
369 (if (= (floor month
) 12) (1+ year
) year
)
370 (calendar-mod (1+ (floor month
)) 12)
372 (m-cycle (%
(+ (* year
5) (floor month
)) 60)))
373 (format "Cycle %s, year %s (%s), %smonth %s%s, day %s (%s)"
375 year
(calendar-chinese-sexagesimal-name year
)
376 (if (not (integerp month
))
378 (if (< 30 (- next-month this-month
))
383 (format " (%s)" (calendar-chinese-sexagesimal-name
384 (+ (* 12 year
) month
50)))
386 day
(calendar-chinese-sexagesimal-name (+ a-date
15)))))
388 (defun calendar-chinese-sexagesimal-name (n)
389 "The N-th name of the Chinese sexagesimal cycle.
390 N congruent to 1 gives the first name, N congruent to 2 gives the second name,
391 ..., N congruent to 60 gives the sixtieth name."
393 (aref chinese-calendar-celestial-stem
(%
(1- n
) 10))
394 (aref chinese-calendar-terrestrial-branch
(%
(1- n
) 12))))
396 (defun calendar-print-chinese-date ()
397 "Show the Chinese date equivalents of date."
399 (message "Computing Chinese date...")
400 (message "Chinese date: %s"
401 (calendar-chinese-date-string (calendar-cursor-to-date t
))))
403 (defun calendar-goto-chinese-date (date &optional noecho
)
404 "Move cursor to Chinese date DATE.
405 Echo Chinese date unless NOECHO is t."
407 (let* ((c (calendar-chinese-from-absolute
408 (calendar-absolute-from-gregorian
409 (calendar-current-date))))
410 (cycle (calendar-read
411 "Chinese calendar cycle number (>44): "
412 '(lambda (x) (> x
44))
413 (int-to-string (car c
))))
415 "Year in Chinese cycle (1..60): "
416 '(lambda (x) (and (<= 1 x
) (<= x
60)))
417 (int-to-string (car (cdr c
)))))
418 (month-list (make-chinese-month-assoc-list
419 (chinese-months cycle year
)))
421 (completing-read "Chinese calendar month: "
426 (calendar-chinese-from-absolute
428 (calendar-absolute-from-chinese
429 (list cycle year month
1))))))))
433 (format "Chinese calendar day (1-%d): " last
)
434 '(lambda (x) (and (<= 1 x
) (<= x last
))))))
435 (list (list cycle year month day
))))
436 (calendar-goto-date (calendar-gregorian-from-absolute
437 (calendar-absolute-from-chinese date
)))
438 (or noecho
(calendar-print-chinese-date)))
440 (defun chinese-months (c y
)
441 "A list of the months in cycle C, year Y of the Chinese calendar."
442 (let* ((l (memq 1 (append
445 (chinese-year (extract-calendar-year
446 (calendar-gregorian-from-absolute
447 (calendar-absolute-from-chinese
450 (if (> (car x
) 11) (car x
)))
451 (chinese-year (extract-calendar-year
452 (calendar-gregorian-from-absolute
453 (calendar-absolute-from-chinese
454 (list (if (= y
60) (1+ c
) c
)
459 (defun make-chinese-month-assoc-list (l)
460 "Make list of months L into an assoc list."
462 (if (and (cdr l
) (car (cdr l
)))
463 (if (= (car l
) (floor (car (cdr l
))))
465 (list (cons (format "%s (first)" (car l
)) (car l
))
466 (cons (format "%s (second)" (car l
)) (car (cdr l
))))
467 (make-chinese-month-assoc-list (cdr (cdr l
))))
469 (list (cons (int-to-string (car l
)) (car l
)))
470 (make-chinese-month-assoc-list (cdr l
))))
471 (list (cons (int-to-string (car l
)) (car l
))))))
473 (defun diary-chinese-date ()
474 "Chinese calendar equivalent of date diary entry."
475 (format "Chinese date: %s" (calendar-chinese-date-string date
)))
479 ;;; cal-china.el ends here