;;; cal-persia.el --- calendar functions for the Persian calendar -*- lexical-binding: t; -*- ;; Copyright (C) 1996-1997, 2001-2021 Free Software Foundation, Inc. ;; Author: Edward M. Reingold ;; Maintainer: emacs-devel@gnu.org ;; Keywords: calendar ;; Human-Keywords: Persian calendar, calendar, diary ;; Package: calendar ;; This file is part of GNU Emacs. ;; GNU Emacs is free software: you can redistribute it and/or modify ;; it under the terms of the GNU General Public License as published by ;; the Free Software Foundation, either version 3 of the License, or ;; (at your option) any later version. ;; GNU Emacs is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; You should have received a copy of the GNU General Public License ;; along with GNU Emacs. If not, see . ;;; Commentary: ;; See calendar.el. ;;; Code: (require 'calendar) (defconst calendar-persian-month-name-array ["Farvardin" "Ordibehest" "Xordad" "Tir" "Mordad" "Sahrivar" "Mehr" "Aban" "Azar" "Dey" "Bahman" "Esfand"] "Names of the months in the Persian calendar.") (eval-and-compile (autoload 'calendar-julian-to-absolute "cal-julian")) (defconst calendar-persian-epoch (eval-when-compile (calendar-julian-to-absolute '(3 19 622))) "Absolute date of start of Persian calendar = March 19, 622 AD (Julian).") (defun calendar-persian-leap-year-p (year) "True if YEAR is a leap year on the Persian calendar." (< (mod (* (mod (mod (if (<= 0 year) (+ year 2346) ; no year zero (+ year 2347)) 2820) 768) 683) 2820) 683)) (defun calendar-persian-last-day-of-month (month year) "Return last day of MONTH, YEAR on the Persian calendar." (cond ((< month 7) 31) ((or (< month 12) (calendar-persian-leap-year-p year)) 30) (t 29))) (defun calendar-persian-to-absolute (date) "Compute absolute date from Persian date DATE. The absolute date is the number of days elapsed since the (imaginary) Gregorian date Sunday, December 31, 1 BC." (let ((month (calendar-extract-month date)) (day (calendar-extract-day date)) (year (calendar-extract-year date))) (if (< year 0) (+ (calendar-persian-to-absolute (list month day (1+ (mod year 2820)))) (* 1029983 (floor year 2820))) (+ (1- calendar-persian-epoch) ; days before epoch (* 365 (1- year)) ; days in prior years (* 683 ; leap days in prior 2820-year cycles (floor (+ year 2345) 2820)) (* 186 ; leap days in prior 768 year cycles (floor (mod (+ year 2345) 2820) 768)) (floor ; leap years in current 768 or 516 year cycle (* 683 (mod (mod (+ year 2345) 2820) 768)) 2820) -568 ; leap years in Persian years -2345...-1 (calendar-sum ; days in prior months this year m 1 (< m month) (calendar-persian-last-day-of-month m year)) day)))) ; days so far this month (defun calendar-persian-year-from-absolute (date) "Persian year corresponding to the absolute DATE." (let* ((d0 ; prior days since start of 2820 cycles (- date (calendar-persian-to-absolute (list 1 1 -2345)))) (n2820 ; completed 2820-year cycles (floor d0 1029983)) (d1 ; prior days not in n2820 (mod d0 1029983)) (n768 ; 768-year cycles not in n2820 (floor d1 280506)) (d2 ; prior days not in n2820 or n768 (mod d1 280506)) (n1 ; years not in n2820 or n768 (floor (* 2820 (+ d2 366)) 1029983)) (year (+ (* 2820 n2820) ; complete 2820 year cycles (* 768 n768) ; complete 768 year cycles ;; Remaining years. (if (= d1 1029617) ; last day of 2820 year cycle (1- n1) n1) -2345))) ; years before year 1 (if (< year 1) (1- year) ; no year zero year))) (defun calendar-persian-from-absolute (date) "Compute the Persian equivalent for absolute date DATE. The result is a list of the form (MONTH DAY YEAR). The absolute date is the number of days elapsed since the imaginary Gregorian date Sunday, December 31, 1 BC." (let* ((year (calendar-persian-year-from-absolute date)) (month ; search forward from Farvardin (1+ (calendar-sum m 1 (> date (calendar-persian-to-absolute (list m (calendar-persian-last-day-of-month m year) year))) 1))) (day ; calculate the day by subtraction (- date (1- (calendar-persian-to-absolute (list month 1 year)))))) (list month day year))) ;;;###cal-autoload (defun calendar-persian-date-string (&optional date) "String of Persian date of Gregorian DATE, default today." (let* ((persian-date (calendar-persian-from-absolute (calendar-absolute-from-gregorian (or date (calendar-current-date))))) (y (calendar-extract-year persian-date)) (m (calendar-extract-month persian-date))) (calendar-dlet* ((monthname (aref calendar-persian-month-name-array (1- m))) (day (number-to-string (calendar-extract-day persian-date))) (year (number-to-string y)) (month (number-to-string m)) dayname) (mapconcat #'eval calendar-date-display-form "")))) ;;;###cal-autoload (defun calendar-persian-print-date () "Show the Persian calendar equivalent of the selected date." (interactive) (message "Persian date: %s" (calendar-persian-date-string (calendar-cursor-to-date t)))) (defun calendar-persian-read-date () "Interactively read the arguments for a Persian date command. Reads a year, month, and day." (let* ((year (calendar-read-sexp "Persian calendar year (not 0)" (lambda (x) (not (zerop x))) (calendar-extract-year (calendar-persian-from-absolute (calendar-absolute-from-gregorian (calendar-current-date)))))) (completion-ignore-case t) (month (cdr (assoc (completing-read "Persian calendar month name: " (mapcar 'list (append calendar-persian-month-name-array nil)) nil t) (calendar-make-alist calendar-persian-month-name-array 1)))) (last (calendar-persian-last-day-of-month month year)) (day (calendar-read-sexp "Persian calendar day (1-%d)" (lambda (x) (and (< 0 x) (<= x last))) nil last))) (list (list month day year)))) ;;;###cal-autoload (defun calendar-persian-goto-date (date &optional noecho) "Move cursor to Persian date DATE. Echo Persian date unless NOECHO is non-nil." (interactive (calendar-persian-read-date)) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-persian-to-absolute date))) (or noecho (calendar-persian-print-date))) ;; The function below is designed to be used in sexp diary entries, ;; and may be present in users' diary files, so suppress the warning ;; about this prefix-less dynamic variable. It's called from ;; `diary-list-sexp-entries', which binds the variable. (with-suppressed-warnings ((lexical date)) (defvar date)) ;;;###diary-autoload (defun diary-persian-date () "Persian calendar equivalent of date diary entry." (format "Persian date: %s" (calendar-persian-date-string date))) (provide 'cal-persia) ;;; cal-persia.el ends here