1;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars 2 3;; Copyright (C) 1995, 1997, 2001, 2002, 2003, 2004, 2005, 2006, 2007 4;; Free Software Foundation, Inc. 5 6;; Author: Edward M. Reingold <reingold@cs.uiuc.edu> 7;; Maintainer: Glenn Morris <rgm@gnu.org> 8;; Keywords: calendar 9;; Human-Keywords: Coptic calendar, Ethiopic calendar, calendar, diary 10 11;; This file is part of GNU Emacs. 12 13;; GNU Emacs is free software; you can redistribute it and/or modify 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) 16;; any later version. 17 18;; GNU Emacs is distributed in the hope that it will be useful, 19;; but WITHOUT ANY WARRANTY; without even the implied warranty of 20;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 21;; GNU General Public License for more details. 22 23;; You should have received a copy of the GNU General Public License 24;; along with GNU Emacs; see the file COPYING. If not, write to the 25;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 26;; Boston, MA 02110-1301, USA. 27 28;;; Commentary: 29 30;; This collection of functions implements the features of calendar.el and 31;; diary.el that deal with the Coptic and Ethiopic calendars. 32 33;; Technical details of all the calendrical calculations can be found in 34;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold 35;; and Nachum Dershowitz, Cambridge University Press (2001). 36 37;;; Code: 38 39(defvar date) 40 41(require 'cal-julian) 42 43(defvar coptic-calendar-month-name-array 44 ["Tut" "Babah" "Hatur" "Kiyahk" "Tubah" "Amshir" "Baramhat" "Barmundah" 45 "Bashans" "Baunah" "Abib" "Misra" "al-Nasi"]) 46 47(defvar coptic-calendar-epoch (calendar-absolute-from-julian '(8 29 284)) 48 "Absolute date of start of Coptic calendar = August 29, 284 A.D. (Julian).") 49 50(defvar coptic-name "Coptic") 51 52(defun coptic-calendar-leap-year-p (year) 53 "True if YEAR is a leap year on the Coptic calendar." 54 (zerop (mod (1+ year) 4))) 55 56(defun coptic-calendar-last-day-of-month (month year) 57 "Return last day of MONTH, YEAR on the Coptic calendar. 58The 13th month is not really a month, but the 5 (6 in leap years) day period of 59Nisi (Kebus) at the end of the year." 60 (if (< month 13) 61 30 62 (if (coptic-calendar-leap-year-p year) 63 6 64 5))) 65 66(defun calendar-absolute-from-coptic (date) 67 "Compute absolute date from Coptic date DATE. 68The absolute date is the number of days elapsed since the (imaginary) 69Gregorian date Sunday, December 31, 1 BC." 70 (let ((month (extract-calendar-month date)) 71 (day (extract-calendar-day date)) 72 (year (extract-calendar-year date))) 73 (+ (1- coptic-calendar-epoch);; Days before start of calendar 74 (* 365 (1- year)) ;; Days in prior years 75 (/ year 4) ;; Leap days in prior years 76 (* 30 (1- month)) ;; Days in prior months this year 77 day))) ;; Days so far this month 78 79 80(defun calendar-coptic-from-absolute (date) 81 "Compute the Coptic equivalent for absolute date DATE. 82The result is a list of the form (MONTH DAY YEAR). 83The absolute date is the number of days elapsed since the imaginary 84Gregorian date Sunday, December 31, 1 BC." 85 (if (< date coptic-calendar-epoch) 86 (list 0 0 0);; pre-Coptic date 87 (let* ((approx (/ (- date coptic-calendar-epoch) 88 366)) ;; Approximation from below. 89 (year ;; Search forward from the approximation. 90 (+ approx 91 (calendar-sum y approx 92 (>= date (calendar-absolute-from-coptic (list 1 1 (1+ y)))) 93 1))) 94 (month ;; Search forward from Tot. 95 (1+ (calendar-sum m 1 96 (> date 97 (calendar-absolute-from-coptic 98 (list m 99 (coptic-calendar-last-day-of-month m year) 100 year))) 101 1))) 102 (day ;; Calculate the day by subtraction. 103 (- date 104 (1- (calendar-absolute-from-coptic (list month 1 year)))))) 105 (list month day year)))) 106 107(defun calendar-coptic-date-string (&optional date) 108 "String of Coptic date of Gregorian DATE. 109Returns the empty string if DATE is pre-Coptic calendar. 110Defaults to today's date if DATE is not given." 111 (let* ((coptic-date (calendar-coptic-from-absolute 112 (calendar-absolute-from-gregorian 113 (or date (calendar-current-date))))) 114 (y (extract-calendar-year coptic-date)) 115 (m (extract-calendar-month coptic-date))) 116 (if (< y 1) 117 "" 118 (let ((monthname (aref coptic-calendar-month-name-array (1- m))) 119 (day (int-to-string (extract-calendar-day coptic-date))) 120 (dayname nil) 121 (month (int-to-string m)) 122 (year (int-to-string y))) 123 (mapconcat 'eval calendar-date-display-form ""))))) 124 125(defun calendar-print-coptic-date () 126 "Show the Coptic calendar equivalent of the selected date." 127 (interactive) 128 (let ((f (calendar-coptic-date-string (calendar-cursor-to-date t)))) 129 (if (string-equal f "") 130 (message "Date is pre-%s calendar" coptic-name) 131 (message "%s date: %s" coptic-name f)))) 132 133(defun calendar-goto-coptic-date (date &optional noecho) 134 "Move cursor to Coptic date DATE. 135Echo Coptic date unless NOECHO is t." 136 (interactive (coptic-prompt-for-date)) 137 (calendar-goto-date (calendar-gregorian-from-absolute 138 (calendar-absolute-from-coptic date))) 139 (or noecho (calendar-print-coptic-date))) 140 141(defun coptic-prompt-for-date () 142 "Ask for a Coptic date." 143 (let* ((today (calendar-current-date)) 144 (year (calendar-read 145 (format "%s calendar year (>0): " coptic-name) 146 '(lambda (x) (> x 0)) 147 (int-to-string 148 (extract-calendar-year 149 (calendar-coptic-from-absolute 150 (calendar-absolute-from-gregorian today)))))) 151 (completion-ignore-case t) 152 (month (cdr (assoc-string 153 (completing-read 154 (format "%s calendar month name: " coptic-name) 155 (mapcar 'list 156 (append coptic-calendar-month-name-array nil)) 157 nil t) 158 (calendar-make-alist coptic-calendar-month-name-array 159 1) t))) 160 (last (coptic-calendar-last-day-of-month month year)) 161 (day (calendar-read 162 (format "%s calendar day (1-%d): " coptic-name last) 163 '(lambda (x) (and (< 0 x) (<= x last)))))) 164 (list (list month day year)))) 165 166(defun diary-coptic-date () 167 "Coptic calendar equivalent of date diary entry." 168 (let ((f (calendar-coptic-date-string date))) 169 (if (string-equal f "") 170 (format "Date is pre-%s calendar" coptic-name) 171 (format "%s date: %s" coptic-name f)))) 172 173(defconst ethiopic-calendar-month-name-array 174 ["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya" 175 "Genbot" "Sane" "Hamle" "Nahas" "Paguem"]) 176 177(defconst ethiopic-calendar-epoch 2796 178 "Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).") 179 180(defconst ethiopic-name "Ethiopic") 181 182(defun calendar-absolute-from-ethiopic (date) 183 "Compute absolute date from Ethiopic date DATE. 184The absolute date is the number of days elapsed since the (imaginary) 185Gregorian date Sunday, December 31, 1 BC." 186 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)) 187 (calendar-absolute-from-coptic date))) 188 189(defun calendar-ethiopic-from-absolute (date) 190 "Compute the Ethiopic equivalent for absolute date DATE. 191The result is a list of the form (MONTH DAY YEAR). 192The absolute date is the number of days elapsed since the imaginary 193Gregorian date Sunday, December 31, 1 BC." 194 (let ((coptic-calendar-epoch ethiopic-calendar-epoch)) 195 (calendar-coptic-from-absolute date))) 196 197(defun calendar-ethiopic-date-string (&optional date) 198 "String of Ethiopic date of Gregorian DATE. 199Returns the empty string if DATE is pre-Ethiopic calendar. 200Defaults to today's date if DATE is not given." 201 (let ((coptic-calendar-epoch ethiopic-calendar-epoch) 202 (coptic-name ethiopic-name) 203 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) 204 (calendar-coptic-date-string date))) 205 206(defun calendar-print-ethiopic-date () 207 "Show the Ethiopic calendar equivalent of the selected date." 208 (interactive) 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 (call-interactively 'calendar-print-coptic-date))) 213 214(defun calendar-goto-ethiopic-date (date &optional noecho) 215 "Move cursor to Ethiopic date DATE. 216Echo Ethiopic date unless NOECHO is t." 217 (interactive 218 (let ((coptic-calendar-epoch ethiopic-calendar-epoch) 219 (coptic-name ethiopic-name) 220 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) 221 (coptic-prompt-for-date))) 222 (calendar-goto-date (calendar-gregorian-from-absolute 223 (calendar-absolute-from-ethiopic date))) 224 (or noecho (calendar-print-ethiopic-date))) 225 226(defun diary-ethiopic-date () 227 "Ethiopic calendar equivalent of date diary entry." 228 (let ((coptic-calendar-epoch ethiopic-calendar-epoch) 229 (coptic-name ethiopic-name) 230 (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) 231 (diary-coptic-date))) 232 233(provide 'cal-coptic) 234 235;;; arch-tag: 72d49161-25df-4072-9312-b182cdca7627 236;;; cal-coptic.el ends here 237