1 ;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars
3 ;; Copyright (C) 1995, 1997, 2001, 2002, 2003, 2004, 2005, 2006, 2007
4 ;; Free Software Foundation, Inc.
6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Maintainer: Glenn Morris <rgm@gnu.org>
9 ;; Human-Keywords: Coptic calendar, Ethiopic calendar, calendar, diary
11 ;; This file is part of XEmacs.
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14 ;; it under the terms of the GNU General Public License as published by
15 ;; the Free Software Foundation; either version 2, or (at your option)
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21 ;; GNU General Public License for more details.
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25 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26 ;; Boston, MA 02110-1301, USA.
28 ;;; Synched up with: FSF Emacs 22 CVS 2007-03-30
32 ;; This collection of functions implements the features of calendar.el and
33 ;; diary.el that deal with the Coptic and Ethiopic calendars.
35 ;; Technical details of all the calendrical calculations can be found in
36 ;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
37 ;; and Nachum Dershowitz, Cambridge University Press (2001).
39 ;; Comments, corrections, and improvements should be sent to
40 ;; Edward M. Reingold Department of Computer Science
41 ;; (217) 333-6733 University of Illinois at Urbana-Champaign
42 ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
43 ;; Urbana, Illinois 61801
51 (defvar coptic-calendar-month-name-array
52 ["Tut" "Babah" "Hatur" "Kiyahk" "Tubah" "Amshir" "Baramhat" "Barmundah"
53 "Bashans" "Baunah" "Abib" "Misra" "al-Nasi"])
55 (defvar coptic-calendar-epoch (calendar-absolute-from-julian '(8 29 284))
56 "Absolute date of start of Coptic calendar = August 29, 284 A.D. (Julian).")
58 (defvar coptic-name "Coptic")
60 (defun coptic-calendar-leap-year-p (year)
61 "True if YEAR is a leap year on the Coptic calendar."
62 (zerop (mod (1+ year) 4)))
64 (defun coptic-calendar-last-day-of-month (month year)
65 "Return last day of MONTH, YEAR on the Coptic calendar.
66 The 13th month is not really a month, but the 5 (6 in leap years) day period of
67 Nisi (Kebus) at the end of the year."
70 (if (coptic-calendar-leap-year-p year)
74 (defun calendar-absolute-from-coptic (date)
75 "Compute absolute date from Coptic date DATE.
76 The absolute date is the number of days elapsed since the (imaginary)
77 Gregorian date Sunday, December 31, 1 BC."
78 (let ((month (extract-calendar-month date))
79 (day (extract-calendar-day date))
80 (year (extract-calendar-year date)))
81 (+ (1- coptic-calendar-epoch);; Days before start of calendar
82 (* 365 (1- year)) ;; Days in prior years
83 (/ year 4) ;; Leap days in prior years
84 (* 30 (1- month)) ;; Days in prior months this year
85 day))) ;; Days so far this month
88 (defun calendar-coptic-from-absolute (date)
89 "Compute the Coptic equivalent for absolute date DATE.
90 The result is a list of the form (MONTH DAY YEAR).
91 The absolute date is the number of days elapsed since the imaginary
92 Gregorian date Sunday, December 31, 1 BC."
93 (if (< date coptic-calendar-epoch)
94 (list 0 0 0);; pre-Coptic date
95 (let* ((approx (/ (- date coptic-calendar-epoch)
96 366)) ;; Approximation from below.
97 (year ;; Search forward from the approximation.
99 (calendar-sum y approx
100 (>= date (calendar-absolute-from-coptic (list 1 1 (1+ y))))
102 (month ;; Search forward from Tot.
103 (1+ (calendar-sum m 1
105 (calendar-absolute-from-coptic
107 (coptic-calendar-last-day-of-month m year)
110 (day ;; Calculate the day by subtraction.
112 (1- (calendar-absolute-from-coptic (list month 1 year))))))
113 (list month day year))))
115 (defun calendar-coptic-date-string (&optional date)
116 "String of Coptic date of Gregorian DATE.
117 Returns the empty string if DATE is pre-Coptic calendar.
118 Defaults to today's date if DATE is not given."
119 (let* ((coptic-date (calendar-coptic-from-absolute
120 (calendar-absolute-from-gregorian
121 (or date (calendar-current-date)))))
122 (y (extract-calendar-year coptic-date))
123 (m (extract-calendar-month coptic-date)))
126 (let ((monthname (aref coptic-calendar-month-name-array (1- m)))
127 (day (int-to-string (extract-calendar-day coptic-date)))
129 (month (int-to-string m))
130 (year (int-to-string y)))
131 (mapconcat 'eval calendar-date-display-form "")))))
133 (defun calendar-print-coptic-date ()
134 "Show the Coptic calendar equivalent of the selected date."
136 (let ((f (calendar-coptic-date-string (calendar-cursor-to-date t))))
137 (if (string-equal f "")
138 (message "Date is pre-%s calendar" coptic-name)
139 (message "%s date: %s" coptic-name f))))
141 (defun calendar-goto-coptic-date (date &optional noecho)
142 "Move cursor to Coptic date DATE.
143 Echo Coptic date unless NOECHO is t."
144 (interactive (coptic-prompt-for-date))
145 (calendar-goto-date (calendar-gregorian-from-absolute
146 (calendar-absolute-from-coptic date)))
147 (or noecho (calendar-print-coptic-date)))
149 (defun coptic-prompt-for-date ()
150 "Ask for a Coptic date."
151 (let* ((today (calendar-current-date))
153 (format "%s calendar year (>0): " coptic-name)
154 '(lambda (x) (> x 0))
156 (extract-calendar-year
157 (calendar-coptic-from-absolute
158 (calendar-absolute-from-gregorian today))))))
159 (completion-ignore-case t)
160 (month (cdr (assoc-string
162 (format "%s calendar month name: " coptic-name)
164 (append coptic-calendar-month-name-array nil))
166 (calendar-make-alist coptic-calendar-month-name-array
168 (last (coptic-calendar-last-day-of-month month year))
170 (format "%s calendar day (1-%d): " coptic-name last)
171 '(lambda (x) (and (< 0 x) (<= x last))))))
172 (list (list month day year))))
174 (defun diary-coptic-date ()
175 "Coptic calendar equivalent of date diary entry."
176 (let ((f (calendar-coptic-date-string date)))
177 (if (string-equal f "")
178 (format "Date is pre-%s calendar" coptic-name)
179 (format "%s date: %s" coptic-name f))))
181 (defconst ethiopic-calendar-month-name-array
182 ["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya"
183 "Genbot" "Sane" "Hamle" "Nahas" "Paguem"])
185 (defconst ethiopic-calendar-epoch 2796
186 "Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).")
188 (defconst ethiopic-name "Ethiopic")
190 (defun calendar-absolute-from-ethiopic (date)
191 "Compute absolute date from Ethiopic date DATE.
192 The absolute date is the number of days elapsed since the (imaginary)
193 Gregorian date Sunday, December 31, 1 BC."
194 (let ((coptic-calendar-epoch ethiopic-calendar-epoch))
195 (calendar-absolute-from-coptic date)))
197 (defun calendar-ethiopic-from-absolute (date)
198 "Compute the Ethiopic equivalent for absolute date DATE.
199 The result is a list of the form (MONTH DAY YEAR).
200 The absolute date is the number of days elapsed since the imaginary
201 Gregorian date Sunday, December 31, 1 BC."
202 (let ((coptic-calendar-epoch ethiopic-calendar-epoch))
203 (calendar-coptic-from-absolute date)))
205 (defun calendar-ethiopic-date-string (&optional date)
206 "String of Ethiopic date of Gregorian DATE.
207 Returns the empty string if DATE is pre-Ethiopic calendar.
208 Defaults to today's date if DATE is not given."
209 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)
210 (coptic-name ethiopic-name)
211 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array))
212 (calendar-coptic-date-string date)))
214 (defun calendar-print-ethiopic-date ()
215 "Show the Ethiopic calendar equivalent of the selected date."
217 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)
218 (coptic-name ethiopic-name)
219 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array))
220 (call-interactively 'calendar-print-coptic-date)))
222 (defun calendar-goto-ethiopic-date (date &optional noecho)
223 "Move cursor to Ethiopic date DATE.
224 Echo Ethiopic date unless NOECHO is t."
226 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)
227 (coptic-name ethiopic-name)
228 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array))
229 (coptic-prompt-for-date)))
230 (calendar-goto-date (calendar-gregorian-from-absolute
231 (calendar-absolute-from-ethiopic date)))
232 (or noecho (calendar-print-ethiopic-date)))
234 (defun diary-ethiopic-date ()
235 "Ethiopic calendar equivalent of date diary entry."
236 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)
237 (coptic-name ethiopic-name)
238 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array))
239 (diary-coptic-date)))
241 (provide 'cal-coptic)
243 ;;; arch-tag: 72d49161-25df-4072-9312-b182cdca7627
244 ;;; cal-coptic.el ends here