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396 lines
16 KiB
EmacsLisp
396 lines
16 KiB
EmacsLisp
;;; lunar.el --- calendar functions for phases of the moon.
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;; Copyright (C) 1992, 1993, 1995, 1997 Free Software Foundation, Inc.
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;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Keywords: calendar
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;; Human-Keywords: moon, lunar phases, calendar, diary
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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 2, or (at your option)
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;; 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; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; This collection of functions implements lunar phases for calendar.el and
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;; diary.el.
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;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
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;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
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;; Willmann-Bell, Inc., 1991.
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;;
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;; WARNING: The calculations will be accurate only to within a few minutes.
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;; The author would be delighted to have an astronomically more sophisticated
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;; person rewrite the code for the lunar calculations in this file!
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;; Technical details of all the calendrical calculations can be found in
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;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
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;; Cambridge University Press (1997).
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;; Comments, corrections, and improvements should be sent to
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;; Edward M. Reingold Department of Computer Science
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;; (217) 333-6733 University of Illinois at Urbana-Champaign
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;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
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;; Urbana, Illinois 61801
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;;; Code:
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(if (fboundp 'atan)
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(require 'lisp-float-type)
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(error "Lunar calculations impossible since floating point is unavailable."))
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(require 'solar)
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(defun lunar-phase-list (month year)
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"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
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(let ((end-month month)
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(end-year year)
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(start-month month)
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(start-year year))
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(increment-calendar-month end-month end-year 3)
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(increment-calendar-month start-month start-year -1)
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(let* ((end-date (list (list end-month 1 end-year)))
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(start-date (list (list start-month
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(calendar-last-day-of-month
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start-month start-year)
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start-year)))
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(index (* 4
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(truncate
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(* 12.3685
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(+ year
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( / (calendar-day-number (list month 1 year))
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366.0)
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-1900)))))
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(new-moon (lunar-phase index))
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(list))
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(while (calendar-date-compare new-moon end-date)
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(if (calendar-date-compare start-date new-moon)
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(setq list (append list (list new-moon))))
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(setq index (1+ index))
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(setq new-moon (lunar-phase index)))
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list)))
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(defun lunar-phase (index)
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"Local date and time of lunar phase INDEX.
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Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
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remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
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3 last quarter."
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(let* ((phase (mod index 4))
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(index (/ index 4.0))
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(time (/ index 1236.85))
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(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
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0.75933
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(* 29.53058868 index)
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(* 0.0001178 time time)
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(* -0.000000155 time time time)
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(* 0.00033
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(solar-sin-degrees (+ 166.56
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(* 132.87 time)
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(* -0.009173 time time))))))
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(sun-anomaly (mod
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(+ 359.2242
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(* 29.105356 index)
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(* -0.0000333 time time)
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(* -0.00000347 time time time))
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360.0))
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(moon-anomaly (mod
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(+ 306.0253
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(* 385.81691806 index)
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(* 0.0107306 time time)
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(* 0.00001236 time time time))
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360.0))
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(moon-lat (mod
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(+ 21.2964
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(* 390.67050646 index)
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(* -0.0016528 time time)
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(* -0.00000239 time time time))
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360.0))
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(adjustment
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(if (memq phase '(0 2))
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(+ (* (- 0.1734 (* 0.000393 time))
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(solar-sin-degrees sun-anomaly))
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(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
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(* -0.4068 (solar-sin-degrees moon-anomaly))
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(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
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(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
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(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
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(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
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(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
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(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
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(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
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(* -0.0006 (solar-sin-degrees
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(+ (* 2 moon-lat) moon-anomaly)))
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(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
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(* 0.0005 (solar-sin-degrees
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(+ (* 2 moon-anomaly) sun-anomaly))))
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(+ (* (- 0.1721 (* 0.0004 time))
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(solar-sin-degrees sun-anomaly))
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(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
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(* -0.6280 (solar-sin-degrees moon-anomaly))
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(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
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(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
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(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
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(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
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(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
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(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
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(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
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(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
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(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
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(* 0.0003 (solar-sin-degrees
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(+ (* 2 moon-anomaly) sun-anomaly)))
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(* 0.0004 (solar-sin-degrees
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(- sun-anomaly (* 2 moon-anomaly))))
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(* -0.0003 (solar-sin-degrees
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(+ (* 2 sun-anomaly) moon-anomaly))))))
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(adj (+ 0.0028
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(* -0.0004 (solar-cosine-degrees
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sun-anomaly))
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(* 0.0003 (solar-cosine-degrees
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moon-anomaly))))
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(adjustment (cond ((= phase 1) (+ adjustment adj))
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((= phase 2) (- adjustment adj))
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(t adjustment)))
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(date (+ date adjustment))
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(date (+ date (/ (- calendar-time-zone
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(solar-ephemeris-correction
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(extract-calendar-year
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(calendar-gregorian-from-absolute
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(truncate date)))))
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60.0 24.0)))
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(time (* 24 (- date (truncate date))))
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(date (calendar-gregorian-from-absolute (truncate date)))
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(adj (dst-adjust-time date time)))
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(list (car adj) (apply 'solar-time-string (cdr adj)) phase)))
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(defun lunar-phase-name (phase)
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"Name of lunar PHASE.
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0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
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(cond ((= 0 phase) "New Moon")
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((= 1 phase) "First Quarter Moon")
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((= 2 phase) "Full Moon")
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((= 3 phase) "Last Quarter Moon")))
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(defun calendar-phases-of-moon ()
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"Create a buffer with the lunar phases for the current calendar window."
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(interactive)
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(message "Computing phases of the moon...")
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(let ((m1 displayed-month)
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(y1 displayed-year)
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(m2 displayed-month)
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(y2 displayed-year))
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(increment-calendar-month m1 y1 -1)
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(increment-calendar-month m2 y2 1)
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(set-buffer (get-buffer-create lunar-phases-buffer))
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(setq buffer-read-only nil)
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(calendar-set-mode-line
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(if (= y1 y2)
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(format "Phases of the Moon from %s to %s, %d%%-"
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(calendar-month-name m1) (calendar-month-name m2) y2)
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(format "Phases of the Moon from %s, %d to %s, %d%%-"
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(calendar-month-name m1) y1 (calendar-month-name m2) y2)))
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(erase-buffer)
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(insert
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(mapconcat
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'(lambda (x)
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(let ((date (car x))
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(time (car (cdr x)))
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(phase (car (cdr (cdr x)))))
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(concat (calendar-date-string date)
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": "
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(lunar-phase-name phase)
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" "
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time)))
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(lunar-phase-list m1 y1) "\n"))
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(goto-char (point-min))
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(set-buffer-modified-p nil)
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(setq buffer-read-only t)
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(display-buffer lunar-phases-buffer)
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(message "Computing phases of the moon...done")))
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;;;###autoload
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(defun phases-of-moon (&optional arg)
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"Display the quarters of the moon for last month, this month, and next month.
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If called with an optional prefix argument, prompts for month and year.
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This function is suitable for execution in a .emacs file."
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(interactive "P")
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(save-excursion
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(let* ((date (if arg
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(calendar-read-date t)
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(calendar-current-date)))
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(displayed-month (extract-calendar-month date))
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(displayed-year (extract-calendar-year date)))
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(calendar-phases-of-moon))))
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(defun diary-phases-of-moon ()
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"Moon phases diary entry."
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(let* ((index (* 4
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(truncate
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(* 12.3685
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(+ (extract-calendar-year date)
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( / (calendar-day-number date)
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366.0)
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-1900)))))
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(phase (lunar-phase index)))
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(while (calendar-date-compare phase (list date))
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(setq index (1+ index))
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(setq phase (lunar-phase index)))
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(if (calendar-date-equal (car phase) date)
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(concat (lunar-phase-name (car (cdr (cdr phase)))) " "
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(car (cdr phase))))))
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;; For the Chinese calendar the calculations for the new moon need to be more
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;; accurate than those above, so we use more terms in the approximation.
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(defun lunar-new-moon-time (k)
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"Astronomical (Julian) day number of K th new moon."
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(let* ((T (/ k 1236.85))
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(T2 (* T T))
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(T3 (* T T T))
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(T4 (* T2 T2))
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(JDE (+ 2451550.09765
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(* 29.530588853 k)
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(* 0.0001337 T2)
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(* -0.000000150 T3)
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(* 0.00000000073 T4)))
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(E (- 1 (* 0.002516 T) (* 0.0000074 T2)))
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(sun-anomaly (+ 2.5534
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(* 29.10535669 k)
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(* -0.0000218 T2)
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(* -0.00000011 T3)))
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(moon-anomaly (+ 201.5643
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(* 385.81693528 k)
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(* 0.0107438 T2)
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(* 0.00001239 T3)
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(* -0.000000058 T4)))
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(moon-argument (+ 160.7108
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(* 390.67050274 k)
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(* -0.0016341 T2)
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(* -0.00000227 T3)
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(* 0.000000011 T4)))
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(omega (+ 124.7746
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(* -1.56375580 k)
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(* 0.0020691 T2)
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(* 0.00000215 T3)))
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(A1 (+ 299.77 (* 0.107408 k) (* -0.009173 T2)))
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(A2 (+ 251.88 (* 0.016321 k)))
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(A3 (+ 251.83 (* 26.641886 k)))
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(A4 (+ 349.42 (* 36.412478 k)))
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(A5 (+ 84.66 (* 18.206239 k)))
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(A6 (+ 141.74 (* 53.303771 k)))
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(A7 (+ 207.14 (* 2.453732 k)))
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(A8 (+ 154.84 (* 7.306860 k)))
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(A9 (+ 34.52 (* 27.261239 k)))
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(A10 (+ 207.19 (* 0.121824 k)))
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(A11 (+ 291.34 (* 1.844379 k)))
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(A12 (+ 161.72 (* 24.198154 k)))
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(A13 (+ 239.56 (* 25.513099 k)))
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(A14 (+ 331.55 (* 3.592518 k)))
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(correction
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(+ (* -0.40720 (solar-sin-degrees moon-anomaly))
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(* 0.17241 E (solar-sin-degrees sun-anomaly))
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(* 0.01608 (solar-sin-degrees (* 2 moon-anomaly)))
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(* 0.01039 (solar-sin-degrees (* 2 moon-argument)))
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(* 0.00739 E (solar-sin-degrees (- moon-anomaly sun-anomaly)))
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(* -0.00514 E (solar-sin-degrees (+ moon-anomaly sun-anomaly)))
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(* 0.00208 E E (solar-sin-degrees (* 2 sun-anomaly)))
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(* -0.00111 (solar-sin-degrees
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(- moon-anomaly (* 2 moon-argument))))
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(* -0.00057 (solar-sin-degrees
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(+ moon-anomaly (* 2 moon-argument))))
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(* 0.00056 E (solar-sin-degrees
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(+ (* 2 moon-anomaly) sun-anomaly)))
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(* -0.00042 (solar-sin-degrees (* 3 moon-anomaly)))
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(* 0.00042 E (solar-sin-degrees
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(+ sun-anomaly (* 2 moon-argument))))
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(* 0.00038 E (solar-sin-degrees
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(- sun-anomaly (* 2 moon-argument))))
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(* -0.00024 E (solar-sin-degrees
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(- (* 2 moon-anomaly) sun-anomaly)))
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(* -0.00017 (solar-sin-degrees omega))
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(* -0.00007 (solar-sin-degrees
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(+ moon-anomaly (* 2 sun-anomaly))))
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(* 0.00004 (solar-sin-degrees
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(- (* 2 moon-anomaly) (* 2 moon-argument))))
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(* 0.00004 (solar-sin-degrees (* 3 sun-anomaly)))
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(* 0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
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(* -2 moon-argument))))
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(* 0.00003 (solar-sin-degrees
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(+ (* 2 moon-anomaly) (* 2 moon-argument))))
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(* -0.00003 (solar-sin-degrees (+ moon-anomaly sun-anomaly
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(* 2 moon-argument))))
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(* 0.00003 (solar-sin-degrees (- moon-anomaly sun-anomaly
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(* -2 moon-argument))))
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(* -0.00002 (solar-sin-degrees (- moon-anomaly sun-anomaly
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(* 2 moon-argument))))
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(* -0.00002 (solar-sin-degrees
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(+ (* 3 moon-anomaly) sun-anomaly)))
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(* 0.00002 (solar-sin-degrees (* 4 moon-anomaly)))))
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(additional
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(+ (* 0.000325 (solar-sin-degrees A1))
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(* 0.000165 (solar-sin-degrees A2))
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(* 0.000164 (solar-sin-degrees A3))
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(* 0.000126 (solar-sin-degrees A4))
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(* 0.000110 (solar-sin-degrees A5))
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(* 0.000062 (solar-sin-degrees A6))
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(* 0.000060 (solar-sin-degrees A7))
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(* 0.000056 (solar-sin-degrees A8))
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(* 0.000047 (solar-sin-degrees A9))
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(* 0.000042 (solar-sin-degrees A10))
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(* 0.000040 (solar-sin-degrees A11))
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(* 0.000037 (solar-sin-degrees A12))
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(* 0.000035 (solar-sin-degrees A13))
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(* 0.000023 (solar-sin-degrees A14))))
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(newJDE (+ JDE correction additional)))
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(+ newJDE
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(- (solar-ephemeris-correction
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(extract-calendar-year
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(calendar-gregorian-from-absolute
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(floor (calendar-absolute-from-astro newJDE))))))
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(/ calendar-time-zone 60.0 24.0))))
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(defun lunar-new-moon-on-or-after (d)
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"Astronomical (Julian) day number of first new moon on or after astronomical
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\(Julian) day number d. The fractional part is the time of day.
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The date and time are local time, including any daylight savings rules,
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as governed by the values of calendar-daylight-savings-starts,
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calendar-daylight-savings-starts-time, calendar-daylight-savings-ends,
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calendar-daylight-savings-ends-time, calendar-daylight-time-offset, and
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calendar-time-zone."
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(let* ((date (calendar-gregorian-from-absolute
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(floor (calendar-absolute-from-astro d))))
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(year (+ (extract-calendar-year date)
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(/ (calendar-day-number date) 365.25)))
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(k (floor (* (- year 2000.0) 12.3685)))
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(date (lunar-new-moon-time k)))
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(while (< date d)
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(setq k (1+ k))
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(setq date (lunar-new-moon-time k)))
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(let* ((a-date (calendar-absolute-from-astro date))
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(time (* 24 (- a-date (truncate a-date))))
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(date (calendar-gregorian-from-absolute (truncate a-date)))
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(adj (dst-adjust-time date time)))
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(calendar-astro-from-absolute
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(+ (calendar-absolute-from-gregorian (car adj))
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(/ (car (cdr adj)) 24.0))))))
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(provide 'lunar)
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;;; lunar.el ends here
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