1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
;;; cal-persia.el --- calendar functions for the Persian calendar
;; Copyright (C) 1996-1997, 2001-2017 Free Software Foundation, Inc.
;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
;; Maintainer: Glenn Morris <rgm@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 <https://www.gnu.org/licenses/>.
;;; 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
;; Want:
;; (floor (+ (* 2820 d2) (* 2820 366)) 1029983))
;; but that causes overflow, so use the following.
;; Use 366 as the divisor because (2820*366 mod 1029983) is small.
(let ((a (floor d2 366))
(b (mod d2 366)))
(+ 1 a (floor (+ (* 2137 a) (* 2820 b) 2137) 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))
(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
"Persian calendar year (not 0): "
(lambda (x) (not (zerop x)))
(number-to-string
(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
(format "Persian calendar day (1-%d): " last)
(lambda (x) (and (< 0 x) (<= x 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)))
(defvar date)
;; To be called from diary-list-sexp-entries, where DATE is bound.
;;;###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
|
