mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-11-28 07:45:00 +00:00
211 lines
8.4 KiB
EmacsLisp
211 lines
8.4 KiB
EmacsLisp
;;; cal-julian.el --- calendar functions for the Julian calendar
|
|
|
|
;; Copyright (C) 1995, 1997 Free Software Foundation, Inc.
|
|
|
|
;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
|
|
;; Keywords: calendar
|
|
;; Human-Keywords: Julian calendar, Julian day number, calendar, diary
|
|
|
|
;; 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 2, 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; see the file COPYING. If not, write to the
|
|
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
|
|
;; Boston, MA 02111-1307, USA.
|
|
|
|
;;; Commentary:
|
|
|
|
;; This collection of functions implements the features of calendar.el and
|
|
;; diary.el that deal with the Julian calendar.
|
|
|
|
;; Technical details of all the calendrical calculations can be found in
|
|
;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
|
|
;; Cambridge University Press (1997).
|
|
|
|
;; Comments, corrections, and improvements should be sent to
|
|
;; Edward M. Reingold Department of Computer Science
|
|
;; (217) 333-6733 University of Illinois at Urbana-Champaign
|
|
;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
|
|
;; Urbana, Illinois 61801
|
|
|
|
;;; Code:
|
|
|
|
(require 'calendar)
|
|
|
|
(defun calendar-julian-from-absolute (date)
|
|
"Compute the Julian (month day year) corresponding to the absolute DATE.
|
|
The absolute date is the number of days elapsed since the (imaginary)
|
|
Gregorian date Sunday, December 31, 1 BC."
|
|
(let* ((approx (/ (+ date 2) 366));; Approximation from below.
|
|
(year ;; Search forward from the approximation.
|
|
(+ approx
|
|
(calendar-sum y approx
|
|
(>= date (calendar-absolute-from-julian (list 1 1 (1+ y))))
|
|
1)))
|
|
(month ;; Search forward from January.
|
|
(1+ (calendar-sum m 1
|
|
(> date
|
|
(calendar-absolute-from-julian
|
|
(list m
|
|
(if (and (= m 2) (= (% year 4) 0))
|
|
29
|
|
(aref [31 28 31 30 31 30 31 31 30 31 30 31]
|
|
(1- m)))
|
|
year)))
|
|
1)))
|
|
(day ;; Calculate the day by subtraction.
|
|
(- date (1- (calendar-absolute-from-julian (list month 1 year))))))
|
|
(list month day year)))
|
|
|
|
(defun calendar-absolute-from-julian (date)
|
|
"The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
|
|
The Gregorian date Sunday, December 31, 1 BC is imaginary."
|
|
(let ((month (extract-calendar-month date))
|
|
(day (extract-calendar-day date))
|
|
(year (extract-calendar-year date)))
|
|
(+ (calendar-day-number date)
|
|
(if (and (= (% year 100) 0)
|
|
(/= (% year 400) 0)
|
|
(> month 2))
|
|
1 0);; Correct for Julian but not Gregorian leap year.
|
|
(* 365 (1- year))
|
|
(/ (1- year) 4)
|
|
-2)))
|
|
|
|
(defun calendar-julian-date-string (&optional date)
|
|
"String of Julian date of Gregorian DATE.
|
|
Defaults to today's date if DATE is not given.
|
|
Driven by the variable `calendar-date-display-form'."
|
|
(calendar-date-string
|
|
(calendar-julian-from-absolute
|
|
(calendar-absolute-from-gregorian
|
|
(or date (calendar-current-date))))
|
|
nil t))
|
|
|
|
(defun calendar-print-julian-date ()
|
|
"Show the Julian calendar equivalent of the date under the cursor."
|
|
(interactive)
|
|
(message "Julian date: %s"
|
|
(calendar-julian-date-string (calendar-cursor-to-date t))))
|
|
|
|
(defun calendar-goto-julian-date (date &optional noecho)
|
|
"Move cursor to Julian DATE; echo Julian date unless NOECHO is t."
|
|
(interactive
|
|
(let* ((today (calendar-current-date))
|
|
(year (calendar-read
|
|
"Julian calendar year (>0): "
|
|
'(lambda (x) (> x 0))
|
|
(int-to-string
|
|
(extract-calendar-year
|
|
(calendar-julian-from-absolute
|
|
(calendar-absolute-from-gregorian
|
|
today))))))
|
|
(month-array calendar-month-name-array)
|
|
(completion-ignore-case t)
|
|
(month (cdr (assoc-ignore-case
|
|
(completing-read
|
|
"Julian calendar month name: "
|
|
(mapcar 'list (append month-array nil))
|
|
nil t)
|
|
(calendar-make-alist month-array 1))))
|
|
(last
|
|
(if (and (zerop (% year 4)) (= month 2))
|
|
29
|
|
(aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
|
|
(day (calendar-read
|
|
(format "Julian calendar day (%d-%d): "
|
|
(if (and (= year 1) (= month 1)) 3 1) last)
|
|
'(lambda (x)
|
|
(and (< (if (and (= year 1) (= month 1)) 2 0) x)
|
|
(<= x last))))))
|
|
(list (list month day year))))
|
|
(calendar-goto-date (calendar-gregorian-from-absolute
|
|
(calendar-absolute-from-julian date)))
|
|
(or noecho (calendar-print-julian-date)))
|
|
|
|
(defun holiday-julian (month day string)
|
|
"Holiday on MONTH, DAY (Julian) called STRING.
|
|
If MONTH, DAY (Julian) is visible, the value returned is corresponding
|
|
Gregorian date in the form of the list (((month day year) STRING)). Returns
|
|
nil if it is not visible in the current calendar window."
|
|
(let ((m1 displayed-month)
|
|
(y1 displayed-year)
|
|
(m2 displayed-month)
|
|
(y2 displayed-year)
|
|
(year))
|
|
(increment-calendar-month m1 y1 -1)
|
|
(increment-calendar-month m2 y2 1)
|
|
(let* ((start-date (calendar-absolute-from-gregorian
|
|
(list m1 1 y1)))
|
|
(end-date (calendar-absolute-from-gregorian
|
|
(list m2 (calendar-last-day-of-month m2 y2) y2)))
|
|
(julian-start (calendar-julian-from-absolute start-date))
|
|
(julian-end (calendar-julian-from-absolute end-date))
|
|
(julian-y1 (extract-calendar-year julian-start))
|
|
(julian-y2 (extract-calendar-year julian-end)))
|
|
(setq year (if (< 10 month) julian-y1 julian-y2))
|
|
(let ((date (calendar-gregorian-from-absolute
|
|
(calendar-absolute-from-julian
|
|
(list month day year)))))
|
|
(if (calendar-date-is-visible-p date)
|
|
(list (list date string)))))))
|
|
|
|
(defun diary-julian-date ()
|
|
"Julian calendar equivalent of date diary entry."
|
|
(format "Julian date: %s" (calendar-julian-date-string date)))
|
|
|
|
(defun calendar-absolute-from-astro (d)
|
|
"Absolute date of astronomical (Julian) day number D."
|
|
(- d 1721424.5))
|
|
|
|
(defun calendar-astro-from-absolute (d)
|
|
"Astronomical (Julian) day number of absolute date D."
|
|
(+ d 1721424.5))
|
|
|
|
(defun calendar-astro-date-string (&optional date)
|
|
"String of astronomical (Julian) day number after noon UTC of Gregorian DATE.
|
|
Defaults to today's date if DATE is not given."
|
|
(int-to-string
|
|
(ceiling
|
|
(calendar-astro-from-absolute
|
|
(calendar-absolute-from-gregorian
|
|
(or date (calendar-current-date)))))))
|
|
|
|
(defun calendar-print-astro-day-number ()
|
|
"Show astronomical (Julian) day number after noon UTC on date shown by cursor."
|
|
(interactive)
|
|
(message
|
|
"Astronomical (Julian) day number (at noon UTC): %s.0"
|
|
(calendar-astro-date-string (calendar-cursor-to-date t))))
|
|
|
|
(defun calendar-goto-astro-day-number (daynumber &optional noecho)
|
|
"Move cursor to astronomical (Julian) DAYNUMBER.
|
|
Echo astronomical (Julian) day number unless NOECHO is t."
|
|
(interactive (list (calendar-read
|
|
"Astronomical (Julian) day number (>1721425): "
|
|
'(lambda (x) (> x 1721425)))))
|
|
(calendar-goto-date
|
|
(calendar-gregorian-from-absolute
|
|
(floor
|
|
(calendar-absolute-from-astro daynumber))))
|
|
(or noecho (calendar-print-astro-day-number)))
|
|
|
|
(defun diary-astro-day-number ()
|
|
"Astronomical (Julian) day number diary entry."
|
|
(format "Astronomical (Julian) day number at noon UTC: %s.0"
|
|
(calendar-astro-date-string date)))
|
|
|
|
(provide 'cal-julian)
|
|
|
|
;;; cal-julian.el ends here
|