210 lines
8.3 KiB
EmacsLisp
210 lines
8.3 KiB
EmacsLisp
;;; cal-persia.el --- calendar functions for the Persian calendar -*- lexical-binding: t; -*-
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;; Copyright (C) 1996-1997, 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: Persian 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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(defconst calendar-persian-month-name-array
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["Farvardin" "Ordibehest" "Xordad" "Tir" "Mordad" "Sahrivar" "Mehr" "Aban"
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"Azar" "Dey" "Bahman" "Esfand"]
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"Names of the months in the Persian calendar.")
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(eval-and-compile
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(autoload 'calendar-julian-to-absolute "cal-julian"))
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(defconst calendar-persian-epoch
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(eval-when-compile (calendar-julian-to-absolute '(3 19 622)))
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"Absolute date of start of Persian calendar = March 19, 622 AD (Julian).")
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(defun calendar-persian-leap-year-p (year)
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"True if YEAR is a leap year on the Persian calendar."
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(< (mod (* (mod (mod (if (<= 0 year)
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(+ year 2346) ; no year zero
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(+ year 2347))
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2820)
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768)
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683)
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2820)
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683))
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(defun calendar-persian-last-day-of-month (month year)
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"Return last day of MONTH, YEAR on the Persian calendar."
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(cond
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((< month 7) 31)
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((or (< month 12) (calendar-persian-leap-year-p year)) 30)
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(t 29)))
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(defun calendar-persian-to-absolute (date)
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"Compute absolute date from Persian 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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(if (< year 0)
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(+ (calendar-persian-to-absolute
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(list month day (1+ (mod year 2820))))
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(* 1029983 (floor year 2820)))
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(+ (1- calendar-persian-epoch) ; days before epoch
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(* 365 (1- year)) ; days in prior years
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(* 683 ; leap days in prior 2820-year cycles
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(floor (+ year 2345) 2820))
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(* 186 ; leap days in prior 768 year cycles
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(floor (mod (+ year 2345) 2820) 768))
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(floor ; leap years in current 768 or 516 year cycle
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(* 683 (mod (mod (+ year 2345) 2820) 768))
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2820)
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-568 ; leap years in Persian years -2345...-1
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(calendar-sum ; days in prior months this year
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m 1 (< m month)
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(calendar-persian-last-day-of-month m year))
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day)))) ; days so far this month
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(defun calendar-persian-year-from-absolute (date)
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"Persian year corresponding to the absolute DATE."
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(let* ((d0 ; prior days since start of 2820 cycles
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(- date (calendar-persian-to-absolute (list 1 1 -2345))))
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(n2820 ; completed 2820-year cycles
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(floor d0 1029983))
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(d1 ; prior days not in n2820
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(mod d0 1029983))
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(n768 ; 768-year cycles not in n2820
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(floor d1 280506))
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(d2 ; prior days not in n2820 or n768
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(mod d1 280506))
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(n1 ; years not in n2820 or n768
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(floor (* 2820 (+ d2 366)) 1029983))
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(year (+ (* 2820 n2820) ; complete 2820 year cycles
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(* 768 n768) ; complete 768 year cycles
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;; Remaining years.
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(if (= d1 1029617) ; last day of 2820 year cycle
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(1- n1)
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n1)
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-2345))) ; years before year 1
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(if (< year 1)
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(1- year) ; no year zero
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year)))
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(defun calendar-persian-from-absolute (date)
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"Compute the Persian 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* ((year (calendar-persian-year-from-absolute date))
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(month ; search forward from Farvardin
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(1+ (calendar-sum m 1
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(> date
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(calendar-persian-to-absolute
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(list
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m
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(calendar-persian-last-day-of-month m 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 (1- (calendar-persian-to-absolute
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(list month 1 year))))))
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(list month day year)))
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;;;###cal-autoload
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(defun calendar-persian-date-string (&optional date)
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"String of Persian date of Gregorian DATE, default today."
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(let* ((persian-date (calendar-persian-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 persian-date))
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(m (calendar-extract-month persian-date)))
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(calendar-dlet
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((monthname (aref calendar-persian-month-name-array (1- m)))
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(day (number-to-string (calendar-extract-day persian-date)))
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(year (number-to-string y))
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(month (number-to-string m))
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dayname)
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(mapconcat #'eval calendar-date-display-form ""))))
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;;;###cal-autoload
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(defun calendar-persian-print-date ()
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"Show the Persian calendar equivalent of the selected date."
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(interactive)
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(message "Persian date: %s"
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(calendar-persian-date-string (calendar-cursor-to-date t))))
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(defun calendar-persian-read-date ()
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"Interactively read the arguments for a Persian date command.
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Reads a year, month, and day."
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(let* ((year (calendar-read-sexp
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"Persian calendar year (not 0)"
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(lambda (x) (not (zerop x)))
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(calendar-extract-year
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(calendar-persian-from-absolute
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(calendar-absolute-from-gregorian
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(calendar-current-date))))))
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(completion-ignore-case t)
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(month (cdr (assoc
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(completing-read
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"Persian calendar month name: "
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(mapcar 'list
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(append calendar-persian-month-name-array nil))
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nil t)
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(calendar-make-alist calendar-persian-month-name-array
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1))))
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(last (calendar-persian-last-day-of-month month year))
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(day (calendar-read-sexp
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"Persian calendar day (1-%d)"
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(lambda (x) (and (< 0 x) (<= x last)))
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nil
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last)))
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(list (list month day year))))
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;;;###cal-autoload
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(defun calendar-persian-goto-date (date &optional noecho)
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"Move cursor to Persian date DATE.
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Echo Persian date unless NOECHO is non-nil."
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(interactive (calendar-persian-read-date))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-persian-to-absolute date)))
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(or noecho (calendar-persian-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-persian-date ()
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"Persian calendar equivalent of date diary entry."
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(format "Persian date: %s" (calendar-persian-date-string date)))
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(provide 'cal-persia)
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;;; cal-persia.el ends here
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