260 lines
10 KiB
EmacsLisp
260 lines
10 KiB
EmacsLisp
;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars -*- lexical-binding: t; -*-
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;; Copyright (C) 1995, 1997, 2001-2024 Free Software Foundation, Inc.
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;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: calendar
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;; Human-Keywords: Coptic calendar, Ethiopic calendar, calendar, diary
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;; Package: calendar
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; See calendar.el.
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;;; Code:
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(require 'calendar)
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;; Not constants because they get let-bound.
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(defvar calendar-coptic-month-name-array
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["Tut" "Babah" "Hatur" "Kiyahk" "Tubah" "Amshir" "Baramhat" "Barmundah"
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"Bashans" "Baunah" "Abib" "Misra" "al-Nasi"]
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"Array of the month names in the Coptic calendar.")
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(eval-and-compile
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(autoload 'calendar-julian-to-absolute "cal-julian"))
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(defvar calendar-coptic-epoch
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(eval-when-compile (calendar-julian-to-absolute '(8 29 284)))
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"Absolute date of start of Coptic calendar = August 29, 284 AD (Julian).")
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(defvar calendar-coptic-name "Coptic"
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"Used in some message strings.")
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(defun calendar-coptic-leap-year-p (year)
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"True if YEAR is a leap year on the Coptic calendar."
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(zerop (mod (1+ year) 4)))
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(defun calendar-coptic-last-day-of-month (month year)
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"Return last day of MONTH, YEAR on the Coptic calendar.
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The 13th month is not really a month, but the 5 (6 in leap years) day period of
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Nisi (Kebus) at the end of the year."
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(if (< month 13)
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30
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(if (calendar-coptic-leap-year-p year)
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6
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5)))
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(defun calendar-coptic-to-absolute (date)
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"Compute absolute date from Coptic date DATE.
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The absolute date is the number of days elapsed since the (imaginary)
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Gregorian date Sunday, December 31, 1 BC."
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(let ((month (calendar-extract-month date))
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(day (calendar-extract-day date))
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(year (calendar-extract-year date)))
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(+ (1- calendar-coptic-epoch) ; days before start of calendar
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(* 365 (1- year)) ; days in prior years
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(/ year 4) ; leap days in prior years
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(* 30 (1- month)) ; days in prior months this year
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day))) ; days so far this month
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(defun calendar-coptic-from-absolute (date)
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"Compute the Coptic equivalent for absolute date DATE.
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The result is a list of the form (MONTH DAY YEAR).
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The absolute date is the number of days elapsed since the imaginary
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Gregorian date Sunday, December 31, 1 BC."
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(if (< date calendar-coptic-epoch)
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(list 0 0 0) ; pre-Coptic date
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(let* ((approx (/ (- date calendar-coptic-epoch)
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366)) ; approximation from below
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(year ; search forward from the approximation
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(+ approx
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(calendar-sum y approx
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(>= date (calendar-coptic-to-absolute
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(list 1 1 (1+ y))))
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1)))
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(month ; search forward from Tot
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(1+ (calendar-sum m 1
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(> date
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(calendar-coptic-to-absolute
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(list m
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(calendar-coptic-last-day-of-month m
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year)
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year)))
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1)))
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(day ; calculate the day by subtraction
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(- date
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(1- (calendar-coptic-to-absolute (list month 1 year))))))
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(list month day year))))
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;;;###cal-autoload
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(defun calendar-coptic-date-string (&optional date)
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"String of Coptic date of Gregorian DATE.
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Returns the empty string if DATE is pre-Coptic calendar.
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Defaults to today's date if DATE is not given."
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(let* ((coptic-date (calendar-coptic-from-absolute
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(calendar-absolute-from-gregorian
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(or date (calendar-current-date)))))
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(y (calendar-extract-year coptic-date))
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(m (calendar-extract-month coptic-date)))
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(if (< y 1)
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""
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(calendar-dlet
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((monthname (aref calendar-coptic-month-name-array (1- m)))
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(day (number-to-string (calendar-extract-day coptic-date)))
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(dayname nil)
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(month (number-to-string m))
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(year (number-to-string y)))
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(mapconcat #'eval calendar-date-display-form "")))))
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;;;###cal-autoload
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(defun calendar-coptic-print-date ()
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"Show the Coptic calendar equivalent of the selected date."
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(interactive)
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(let ((f (calendar-coptic-date-string (calendar-cursor-to-date t))))
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(if (string-equal f "")
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(message "Date is pre-%s calendar" calendar-coptic-name)
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(message "%s date: %s" calendar-coptic-name f))))
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(defun calendar-coptic-read-date ()
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"Interactively read the arguments for a Coptic date command.
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Reads a year, month, and day."
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(let* ((today (calendar-current-date))
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(year (calendar-read-sexp
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"%s calendar year (>0)"
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(lambda (x) (> x 0))
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(calendar-extract-year
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(calendar-coptic-from-absolute
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(calendar-absolute-from-gregorian today)))
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calendar-coptic-name))
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(completion-ignore-case t)
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(month (cdr (assoc-string
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(completing-read
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(format "%s calendar month name: " calendar-coptic-name)
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(mapcar 'list
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(append calendar-coptic-month-name-array nil))
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nil t)
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(calendar-make-alist calendar-coptic-month-name-array
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1)
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t)))
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(last (calendar-coptic-last-day-of-month month year))
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(day (calendar-read-sexp
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"%s calendar day (1-%d)"
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(lambda (x) (and (< 0 x) (<= x last)))
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nil
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calendar-coptic-name last)))
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(list (list month day year))))
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;;;###cal-autoload
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(defun calendar-coptic-goto-date (date &optional noecho)
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"Move cursor to Coptic date DATE.
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Echo Coptic date unless NOECHO is t."
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(interactive (calendar-coptic-read-date))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-coptic-to-absolute date)))
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(or noecho (calendar-coptic-print-date)))
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;; The function below is designed to be used in sexp diary entries,
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;; and may be present in users' diary files, so suppress the warning
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;; about this prefix-less dynamic variable. It's called from
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;; `diary-list-sexp-entries', which binds the variable.
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(with-suppressed-warnings ((lexical date))
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(defvar date))
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;;;###diary-autoload
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(defun diary-coptic-date ()
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"Coptic calendar equivalent of date diary entry."
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(let ((f (calendar-coptic-date-string date)))
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(if (string-equal f "")
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(format "Date is pre-%s calendar" calendar-coptic-name)
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(format "%s date: %s" calendar-coptic-name f))))
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(defconst calendar-ethiopic-month-name-array
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["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya"
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"Genbot" "Sane" "Hamle" "Nahas" "Paguem"]
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"Array of the month names in the Ethiopic calendar.")
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(defconst calendar-ethiopic-epoch 2796
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"Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).")
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(defconst calendar-ethiopic-name "Ethiopic"
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"Used in some message strings.")
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(defun calendar-ethiopic-to-absolute (thedate)
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"Compute absolute date from Ethiopic date DATE.
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The absolute date is the number of days elapsed since the (imaginary)
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Gregorian date Sunday, December 31, 1 BC."
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch))
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(calendar-coptic-to-absolute thedate)))
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(defun calendar-ethiopic-from-absolute (thedate)
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"Compute the Ethiopic equivalent for absolute date DATE.
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The result is a list of the form (MONTH DAY YEAR).
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The absolute date is the number of days elapsed since the imaginary
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Gregorian date Sunday, December 31, 1 BC."
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch))
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(calendar-coptic-from-absolute thedate)))
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;;;###cal-autoload
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(defun calendar-ethiopic-date-string (&optional thedate)
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"String of Ethiopic date of Gregorian DATE.
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Returns the empty string if DATE is pre-Ethiopic calendar.
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Defaults to today's date if DATE is not given."
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch)
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(calendar-coptic-name calendar-ethiopic-name)
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(calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
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(calendar-coptic-date-string thedate)))
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;;;###cal-autoload
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(defun calendar-ethiopic-print-date ()
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"Show the Ethiopic calendar equivalent of the selected date."
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(interactive)
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch)
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(calendar-coptic-name calendar-ethiopic-name)
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(calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
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(call-interactively 'calendar-coptic-print-date)))
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;;;###cal-autoload
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(defun calendar-ethiopic-goto-date (thedate &optional noecho)
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"Move cursor to Ethiopic date THEDATE.
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Echo Ethiopic date unless NOECHO is t."
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(interactive
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch)
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(calendar-coptic-name calendar-ethiopic-name)
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(calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
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(calendar-coptic-read-date)))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-ethiopic-to-absolute thedate)))
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(or noecho (calendar-ethiopic-print-date)))
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;; To be called from diary-list-sexp-entries, where DATE is bound.
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;;;###diary-autoload
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(defun diary-ethiopic-date ()
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"Ethiopic calendar equivalent of date diary entry."
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(let ((calendar-coptic-epoch calendar-ethiopic-epoch)
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(calendar-coptic-name calendar-ethiopic-name)
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(calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
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(diary-coptic-date)))
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(provide 'cal-coptic)
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;;; cal-coptic.el ends here
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