mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-03 08:30:09 +00:00
c68488d2f7
(solar-time-string): Rewritten. (solar-adj-time-for-dst): New function. (solar-sunrise-sunset, diary-sabbath-candles, solar-equinoxes-solstices): Revised to use the rewritten and new fcns.
541 lines
21 KiB
EmacsLisp
541 lines
21 KiB
EmacsLisp
;;; solar.el --- calendar functions for solar events.
|
|
|
|
;; Copyright (C) 1992, 1993 Free Software Foundation, Inc.
|
|
|
|
;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
|
|
;; Keywords: calendar
|
|
;; Human-Keywords: sunrise, sunset, equinox, solstice, calendar, diary,
|
|
;; holidays
|
|
|
|
;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
|
|
;;; Commentary:
|
|
|
|
;; This collection of functions implements the features of calendar.el and
|
|
;; diary.el that deal with times of day, sunrise/sunset, and
|
|
;; eqinoxes/solstices.
|
|
|
|
;; Based on the ``Almanac for Computers 1984,'' prepared by the Nautical
|
|
;; Almanac Office, United States Naval Observatory, Washington, 1984 and
|
|
;; on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
|
|
;; Willmann-Bell, Inc., 1985.
|
|
;;
|
|
;; WARNINGS:
|
|
;; 1. SUNRISE/SUNSET calculations will be accurate only to +/- 2 minutes.
|
|
;; Locations should be between +/- 65 degrees of latitude.
|
|
;; Dates should be in the latter half of the 20th century.
|
|
;;
|
|
;; 2. Equinox/solstice times will be accurate only to +/- 15 minutes.
|
|
|
|
;; The author would be delighted to have an astronomically more sophisticated
|
|
;; person rewrite the code for the solar calculations in this file!
|
|
|
|
;; 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:
|
|
|
|
(if (fboundp 'atan)
|
|
(require 'lisp-float-type)
|
|
(error "Solar calculations impossible since floating point is unavailable."))
|
|
|
|
(require 'cal-dst)
|
|
|
|
;;;###autoload
|
|
(defvar calendar-time-display-form
|
|
'(12-hours ":" minutes am-pm
|
|
(if time-zone " (") time-zone (if time-zone ")"))
|
|
"*The pseudo-pattern that governs the way a time of day is formatted.
|
|
|
|
A pseudo-pattern is a list of expressions that can involve the keywords
|
|
`12-hours', `24-hours', and `minutes', all numbers in string form,
|
|
and `am-pm' and `time-zone', both alphabetic strings.
|
|
|
|
For example, the form
|
|
|
|
'(24-hours \":\" minutes
|
|
(if time-zone \" (\") time-zone (if time-zone \")\"))
|
|
|
|
would give military-style times like `21:07 (UTC)'.")
|
|
|
|
;;;###autoload
|
|
(defvar calendar-latitude nil
|
|
"*Latitude of `calendar-location-name' in degrees, + north, - south.
|
|
For example, 40.7 for New York City.
|
|
It may not be a good idea to set this in advance for your site;
|
|
if there may be users running Emacs at your site
|
|
who are physically located elsewhere, they would get the wrong
|
|
value and might not know how to override it.")
|
|
|
|
;;;###autoload
|
|
(defvar calendar-longitude nil
|
|
"*Longitude of `calendar-location-name' in degrees, + east, - west.
|
|
For example, -74.0 for New York City.
|
|
It may not be a good idea to set this in advance for your site;
|
|
if there may be users running Emacs at your site
|
|
who are physically located elsewhere, they would get the wrong
|
|
value and might not know how to override it.")
|
|
|
|
;;;###autoload
|
|
(defvar calendar-location-name
|
|
'(let ((float-output-format "%.1f"))
|
|
(format "%s%s, %s%s"
|
|
(abs calendar-latitude)
|
|
(if (> calendar-latitude 0) "N" "S")
|
|
(abs calendar-longitude)
|
|
(if (> calendar-longitude 0) "E" "W")))
|
|
"*Expression evaluating to name of `calendar-longitude', calendar-latitude'.
|
|
Default value is just the latitude, longitude pair.")
|
|
|
|
(defvar solar-n-hemi-seasons
|
|
'("Vernal Equinox" "Summer Solstice" "Autumnal Equinox" "Winter Solstice")
|
|
"List of season changes for the northern hemisphere.")
|
|
|
|
(defvar solar-s-hemi-seasons
|
|
'("Autumnal Equinox" "Winter Solstice" "Vernal Equinox" "Summer Solstice")
|
|
"List of season changes for the southern hemisphere.")
|
|
|
|
(defun solar-setup ()
|
|
"Prompt user for latitude, longitude, and time zone."
|
|
(beep)
|
|
(if (not calendar-longitude)
|
|
(setq calendar-longitude
|
|
(solar-get-number
|
|
"Enter longitude (decimal fraction; + east, - west): ")))
|
|
(if (not calendar-latitude)
|
|
(setq calendar-latitude
|
|
(solar-get-number
|
|
"Enter latitude (decimal fraction; + north, - south): ")))
|
|
(if (not calendar-time-zone)
|
|
(setq calendar-time-zone
|
|
(solar-get-number
|
|
"Enter difference from Coordinated Universal Time (in minutes): "))))
|
|
|
|
(defun solar-get-number (prompt)
|
|
"Return a number from the minibuffer, prompting with PROMPT.
|
|
Returns nil if nothing was entered."
|
|
(let ((x (read-string prompt "")))
|
|
(if (not (string-equal x ""))
|
|
(string-to-int x))))
|
|
|
|
(defun solar-sin-degrees (x)
|
|
(sin (degrees-to-radians x)))
|
|
|
|
(defun solar-cosine-degrees (x)
|
|
(cos (degrees-to-radians x)))
|
|
|
|
(defun solar-tangent-degrees (x)
|
|
(tan (degrees-to-radians x)))
|
|
|
|
(defun solar-xy-to-quadrant (x y)
|
|
"Determines the quadrant of the point X, Y."
|
|
(if (> x 0)
|
|
(if (> y 0) 1 4)
|
|
(if (> y 0) 2 3)))
|
|
|
|
(defun solar-degrees-to-quadrant (angle)
|
|
"Determines the quadrant of ANGLE."
|
|
(1+ (floor (mod angle 360) 90)))
|
|
|
|
(defun solar-arctan (x quad)
|
|
"Arctangent of X in quadrant QUAD."
|
|
(let ((deg (radians-to-degrees (atan x))))
|
|
(cond ((equal quad 2) (+ deg 180))
|
|
((equal quad 3) (+ deg 180))
|
|
((equal quad 4) (+ deg 360))
|
|
(t deg))))
|
|
|
|
(defun solar-arccos (x)
|
|
(let ((y (sqrt (- 1 (* x x)))))
|
|
(solar-arctan (/ y x) (solar-xy-to-quadrant x y))))
|
|
|
|
(defun solar-arcsin (y)
|
|
(let ((x (sqrt (- 1 (* y y)))))
|
|
(solar-arctan (/ y x) (solar-xy-to-quadrant x y))))
|
|
|
|
(defconst solar-earth-inclination 23.441884
|
|
"Inclination of earth's equator to its solar orbit in degrees.")
|
|
|
|
(defconst solar-cos-inclination (solar-cosine-degrees solar-earth-inclination)
|
|
"Cosine of earth's inclination.")
|
|
|
|
(defconst solar-sin-inclination (solar-sin-degrees solar-earth-inclination)
|
|
"Sine of earth's inclination.")
|
|
|
|
(defconst solar-earth-orbit-eccentricity 0.016718
|
|
"Eccentricity of orbit of the earth around the sun.")
|
|
|
|
(defmacro solar-degrees-to-hours (deg)
|
|
(list '/ deg 15.0))
|
|
|
|
(defmacro solar-hours-to-days (hour)
|
|
(list '/ hour 24.0))
|
|
|
|
(defun solar-longitude-of-sun (day)
|
|
"Longitude of the sun at DAY in the year."
|
|
(let ((mean-anomaly (- (* 0.9856 day) 3.289)))
|
|
(mod (+ mean-anomaly
|
|
(* 1.916 (solar-sin-degrees mean-anomaly))
|
|
(* 0.020 (solar-sin-degrees (* 2 mean-anomaly)))
|
|
282.634)
|
|
360)))
|
|
|
|
(defun solar-right-ascension (longitude)
|
|
"Right ascension of the sun, given its LONGITUDE."
|
|
(solar-degrees-to-hours
|
|
(solar-arctan
|
|
(* solar-cos-inclination (solar-tangent-degrees longitude))
|
|
(solar-degrees-to-quadrant longitude))))
|
|
|
|
(defun solar-declination (longitude)
|
|
"Declination of the sun, given its LONGITUDE."
|
|
(solar-arcsin
|
|
(* solar-sin-inclination
|
|
(solar-sin-degrees longitude))))
|
|
|
|
(defun solar-sunrise (date)
|
|
"Calculates the *standard* time of sunrise for Gregorian DATE.
|
|
Calculation is for location given by `calendar-latitude' and
|
|
`calendar-longitude'.
|
|
|
|
Returns a decimal fraction of hours. Returns nil if the sun does not rise at
|
|
that location on that day."
|
|
(let* ((day-of-year (calendar-day-number date))
|
|
(approx-sunrise
|
|
(+ day-of-year
|
|
(solar-hours-to-days
|
|
(- 6 (solar-degrees-to-hours calendar-longitude)))))
|
|
(solar-longitude-of-sun-at-sunrise
|
|
(solar-longitude-of-sun approx-sunrise))
|
|
(solar-right-ascension-at-sunrise
|
|
(solar-right-ascension solar-longitude-of-sun-at-sunrise))
|
|
(solar-declination-at-sunrise
|
|
(solar-declination solar-longitude-of-sun-at-sunrise))
|
|
(cos-local-sunrise
|
|
(/ (- (solar-cosine-degrees (+ 90 (/ 50.0 60.0)))
|
|
(* (solar-sin-degrees solar-declination-at-sunrise)
|
|
(solar-sin-degrees calendar-latitude)))
|
|
(* (solar-cosine-degrees solar-declination-at-sunrise)
|
|
(solar-cosine-degrees calendar-latitude)))))
|
|
(if (<= (abs cos-local-sunrise) 1);; otherwise, no sunrise that day
|
|
(let* ((local-sunrise (solar-degrees-to-hours
|
|
(- 360 (solar-arccos cos-local-sunrise))))
|
|
(local-mean-sunrise
|
|
(mod (- (+ local-sunrise solar-right-ascension-at-sunrise)
|
|
(+ (* 0.065710 approx-sunrise)
|
|
6.622))
|
|
24)))
|
|
(+ (- local-mean-sunrise (solar-degrees-to-hours calendar-longitude))
|
|
(/ calendar-time-zone 60.0))))))
|
|
|
|
(defun solar-sunset (date)
|
|
"Calculates the *standard* time of sunset for Gregorian DATE.
|
|
Calculation is for location given by `calendar-latitude' and
|
|
`calendar-longitude'.
|
|
|
|
Returns a decimal fractions of hours. Returns nil if the sun does not set at
|
|
that location on that day."
|
|
(let* ((day-of-year (calendar-day-number date))
|
|
(approx-sunset
|
|
(+ day-of-year
|
|
(solar-hours-to-days
|
|
(- 18 (solar-degrees-to-hours calendar-longitude)))))
|
|
(solar-longitude-of-sun-at-sunset
|
|
(solar-longitude-of-sun approx-sunset))
|
|
(solar-right-ascension-at-sunset
|
|
(solar-right-ascension solar-longitude-of-sun-at-sunset))
|
|
(solar-declination-at-sunset
|
|
(solar-declination solar-longitude-of-sun-at-sunset))
|
|
(cos-local-sunset
|
|
(/ (- (solar-cosine-degrees (+ 90 (/ 50.0 60.0)))
|
|
(* (solar-sin-degrees solar-declination-at-sunset)
|
|
(solar-sin-degrees calendar-latitude)))
|
|
(* (solar-cosine-degrees solar-declination-at-sunset)
|
|
(solar-cosine-degrees calendar-latitude)))))
|
|
(if (<= (abs cos-local-sunset) 1);; otherwise, no sunset that day
|
|
(let* ((local-sunset (solar-degrees-to-hours
|
|
(solar-arccos cos-local-sunset)))
|
|
(local-mean-sunset
|
|
(mod (- (+ local-sunset solar-right-ascension-at-sunset)
|
|
(+ (* 0.065710 approx-sunset) 6.622))
|
|
24)))
|
|
(+ (- local-mean-sunset (solar-degrees-to-hours calendar-longitude))
|
|
(/ calendar-time-zone 60.0))))))
|
|
|
|
(defun solar-adj-time-for-dst (date time &optional style)
|
|
"Adjust decimal fraction standard TIME on DATE to account for dst.
|
|
Returns a list (date adj-time zone) where `date' and `time' are the values
|
|
adjusted for `zone'; here `date' is a list (month day year), `time' is a
|
|
decimal fraction time, and `zone' is a string.
|
|
|
|
Optional parameter STYLE forces the result time to be standard time when its
|
|
value is 'standard and daylight savings time (if available) when its value is
|
|
'daylight.
|
|
|
|
Conversion to daylight savings time is done according to
|
|
`calendar-daylight-savings-starts', `calendar-daylight-savings-ends',
|
|
`calendar-daylight-savings-starts-time',
|
|
`calendar-daylight-savings-ends-time', and
|
|
`calendar-daylight-savings-offset'."
|
|
|
|
(let* ((year (extract-calendar-year date))
|
|
(rounded-abs-date (+ (calendar-absolute-from-gregorian date)
|
|
(/ (round (* 60 time)) 60.0 24.0)))
|
|
(dst-starts (and calendar-daylight-savings-starts
|
|
(+ (calendar-absolute-from-gregorian
|
|
(eval calendar-daylight-savings-starts))
|
|
(/ calendar-daylight-savings-starts-time
|
|
60.0 24.0))))
|
|
(dst-ends (and calendar-daylight-savings-ends
|
|
(+ (calendar-absolute-from-gregorian
|
|
(eval calendar-daylight-savings-ends))
|
|
(/ (- calendar-daylight-savings-ends-time
|
|
calendar-daylight-time-offset)
|
|
60.0 24.0))))
|
|
(dst (and (not (eq style 'standard))
|
|
(or (eq style 'daylight)
|
|
(and dst-starts dst-ends
|
|
(or (and (< dst-starts dst-ends);; northern hemi.
|
|
(<= dst-starts rounded-abs-date)
|
|
(< rounded-abs-date dst-ends))
|
|
(and (< dst-ends dst-starts);; southern hemi.
|
|
(or (< rounded-abs-date dst-ends)
|
|
(<= dst-starts rounded-abs-date)))))
|
|
(and dst-starts (not dst-ends)
|
|
(<= dst-starts rounded-abs-date))
|
|
(and dst-ends (not dst-starts)
|
|
(< rounded-abs-date dst-ends)))))
|
|
(time-zone (if dst
|
|
calendar-daylight-time-zone-name
|
|
calendar-standard-time-zone-name))
|
|
(time (+ rounded-abs-date
|
|
(if dst (/ calendar-daylight-time-offset 24.0 60.0) 0))))
|
|
(list (calendar-gregorian-from-absolute (truncate time))
|
|
(* 24.0 (- time (truncate time)))
|
|
time-zone)))
|
|
|
|
(defun solar-time-string (time time-zone)
|
|
"Printable form for decimal fraction TIME on DATE.
|
|
Format used is given by `calendar-time-display-form'."
|
|
(let* ((time (round (* 60 time)))
|
|
(24-hours (/ time 60))
|
|
(minutes (format "%02d" (% time 60)))
|
|
(12-hours (format "%d" (1+ (% (+ 24-hours 11) 12))))
|
|
(am-pm (if (>= 24-hours 12) "pm" "am"))
|
|
(24-hours (format "%02d" 24-hours)))
|
|
(mapconcat 'eval calendar-time-display-form "")))
|
|
|
|
(defun solar-sunrise-sunset (date)
|
|
"String giving local times of sunrise and sunset on Gregorian DATE."
|
|
(let* ((rise (solar-sunrise date))
|
|
(adj-rise (solar-adj-time-for-dst date rise))
|
|
(set (solar-sunset date))
|
|
(adj-set (solar-adj-time-for-dst date set)))
|
|
(format "%s, %s at %s"
|
|
(if (and rise (calendar-date-equal date (car adj-rise)))
|
|
(concat "Sunrise " (apply 'solar-time-string (cdr adj-rise)))
|
|
"No sunrise")
|
|
(if (and set (calendar-date-equal date (car adj-set)))
|
|
(concat "sunset " (apply 'solar-time-string (cdr adj-set)))
|
|
"no sunset")
|
|
(eval calendar-location-name))))
|
|
|
|
(defun solar-apparent-longitude-of-sun (date)
|
|
"Apparent longitude of the sun on Gregorian DATE."
|
|
(let* ((time (/ (- (calendar-absolute-from-gregorian date)
|
|
(calendar-absolute-from-gregorian '(1 0.5 1900)))
|
|
36525))
|
|
(l (+ 279.69668
|
|
(* 36000.76892 time)
|
|
(* 0.0003025 time time)))
|
|
(m (+ 358.47583
|
|
(* 35999.04975 time)
|
|
(* -0.000150 time time)
|
|
(* -0.0000033 time time time)))
|
|
(c (+ (* (+ 1.919460
|
|
(* -0.004789 time)
|
|
(* -0.000014 time time))
|
|
(solar-sin-degrees m))
|
|
(* (+ 0.020094
|
|
(* -0.000100 time))
|
|
(solar-sin-degrees (* 2 m)))
|
|
(* 0.000293
|
|
(solar-sin-degrees (* 3 m)))))
|
|
(L (+ l c))
|
|
(omega (+ 259.18
|
|
(* -1934.142 time)))
|
|
(app (+ L
|
|
-0.00569
|
|
(* -0.00479
|
|
(solar-sin-degrees omega)))))
|
|
app))
|
|
|
|
(defun solar-ephemeris-correction (year)
|
|
"Difference in minutes between Ephemeris time and UTC in YEAR.
|
|
Value is only an approximation."
|
|
(let ((T (/ (- year 1900) 100.0)))
|
|
(+ 0.41 (* 1.2053 T) (* 0.4992 T T))))
|
|
|
|
(defun solar-equinoxes/solstices (k year)
|
|
"Date of equinox/solstice K for YEAR. K=0, spring equinox; K=1, summer
|
|
solstice; K=2, fall equinox; K=3, winter solstice. Accurate to within
|
|
several minutes."
|
|
(let ((date (list (+ 3 (* k 3)) 21 year))
|
|
app
|
|
(correction 1000))
|
|
(while (> correction 0.00001)
|
|
(setq app (mod (solar-apparent-longitude-of-sun date) 360))
|
|
(setq correction (* 58 (solar-sin-degrees (- (* k 90) app))))
|
|
(setq date (list (extract-calendar-month date)
|
|
(+ (extract-calendar-day date) correction)
|
|
year)))
|
|
(list (extract-calendar-month date)
|
|
(+ (extract-calendar-day date) (/ calendar-time-zone 60.0 24.0)
|
|
(- (/ (solar-ephemeris-correction year) 60.0 24.0)))
|
|
year)))
|
|
|
|
;;;###autoload
|
|
(defun sunrise-sunset (&optional arg)
|
|
"Local time of sunrise and sunset for today. Accurate to +/- 2 minutes.
|
|
If called with an optional prefix argument, prompt for date.
|
|
|
|
If called with an optional double prefix argument, prompt for longitude,
|
|
latitude, time zone, and date, and always use standard time.
|
|
|
|
This function is suitable for execution in a .emacs file."
|
|
(interactive "p")
|
|
(or arg (setq arg 1))
|
|
(if (and (< arg 16)
|
|
(not (and calendar-latitude calendar-longitude calendar-time-zone)))
|
|
(solar-setup))
|
|
(let* ((calendar-longitude
|
|
(if (< arg 16) calendar-longitude
|
|
(solar-get-number
|
|
"Enter longitude (decimal fraction; + east, - west): ")))
|
|
(calendar-latitude
|
|
(if (< arg 16) calendar-latitude
|
|
(solar-get-number
|
|
"Enter latitude (decimal fraction; + north, - south): ")))
|
|
(calendar-time-zone
|
|
(if (< arg 16) calendar-time-zone
|
|
(solar-get-number
|
|
"Enter difference from Coordinated Universal Time (in minutes): ")))
|
|
(calendar-location-name
|
|
(if (< arg 16) calendar-location-name
|
|
(let ((float-output-format "%.1f"))
|
|
(format "%s%s, %s%s"
|
|
(abs calendar-latitude)
|
|
(if (> calendar-latitude 0) "N" "S")
|
|
(abs calendar-longitude)
|
|
(if (> calendar-longitude 0) "E" "W")))))
|
|
(calendar-standard-time-zone-name
|
|
(if (< arg 16) calendar-standard-time-zone-name
|
|
(cond ((= calendar-time-zone 0) "UTC")
|
|
((< calendar-time-zone 0)
|
|
(format "UTC%dmin" calendar-time-zone))
|
|
(t (format "UTC+%dmin" calendar-time-zone)))))
|
|
(calendar-daylight-savings-starts
|
|
(if (< arg 16) calendar-daylight-savings-starts))
|
|
(calendar-daylight-savings-ends
|
|
(if (< arg 16) calendar-daylight-savings-ends))
|
|
(date (if (< arg 4) (calendar-current-date) (calendar-read-date)))
|
|
(date-string (calendar-date-string date t))
|
|
(time-string (solar-sunrise-sunset date))
|
|
(msg (format "%s: %s" date-string time-string))
|
|
(one-window (one-window-p t)))
|
|
(if (<= (length msg) (frame-width))
|
|
(message msg)
|
|
(with-output-to-temp-buffer "*temp*"
|
|
(princ (concat date-string "\n" time-string)))
|
|
(message (substitute-command-keys
|
|
(if one-window
|
|
(if pop-up-windows
|
|
"Type \\[delete-other-windows] to remove temp window."
|
|
"Type \\[switch-to-buffer] RET to remove temp window.")
|
|
"Type \\[switch-to-buffer-other-window] RET to restore old contents of temp window."))))))
|
|
|
|
(defun calendar-sunrise-sunset ()
|
|
"Local time of sunrise and sunset for date under cursor.
|
|
Accurate to +/- 2 minutes."
|
|
(interactive)
|
|
(if (not (and calendar-latitude calendar-longitude calendar-time-zone))
|
|
(solar-setup))
|
|
(let ((date (calendar-cursor-to-date t)))
|
|
(message "%s: %s"
|
|
(calendar-date-string date t t)
|
|
(solar-sunrise-sunset date))))
|
|
|
|
(defun diary-sunrise-sunset ()
|
|
"Local time of sunrise and sunset as a diary entry.
|
|
Accurate to +/- 2 minutes."
|
|
(if (not (and calendar-latitude calendar-longitude calendar-time-zone))
|
|
(solar-setup))
|
|
(solar-sunrise-sunset date))
|
|
|
|
(defun diary-sabbath-candles ()
|
|
"Local time of candle lighting diary entry--applies if date is a Friday.
|
|
No diary entry if there is no sunset on that date."
|
|
(if (not (and calendar-latitude calendar-longitude calendar-time-zone))
|
|
(solar-setup))
|
|
(if (= (% (calendar-absolute-from-gregorian date) 7) 5);; Friday
|
|
(let* ((sunset (solar-sunset date))
|
|
(light (if sunset
|
|
(solar-adj-time-for-dst
|
|
date
|
|
(- sunset (/ 18.0 60.0))))))
|
|
(if (and light (calendar-date-equal date (car light)))
|
|
(format "%s Sabbath candle lighting"
|
|
(apply 'solar-time-string (cdr light)))))))
|
|
|
|
;;;###autoload
|
|
(defun solar-equinoxes-solstices ()
|
|
"Date and time of equinoxes and solstices, if visible in the calendar window.
|
|
Requires floating point."
|
|
(let ((m displayed-month)
|
|
(y displayed-year))
|
|
(increment-calendar-month m y (cond ((= 1 (% m 3)) -1)
|
|
((= 2 (% m 3)) 1)
|
|
(t 0)))
|
|
(let* ((calendar-standard-time-zone-name
|
|
(if calendar-time-zone calendar-standard-time-zone-name "UTC"))
|
|
(calendar-daylight-savings-starts
|
|
(if calendar-time-zone calendar-daylight-savings-starts))
|
|
(calendar-daylight-savings-ends
|
|
(if calendar-time-zone calendar-daylight-savings-ends))
|
|
(calendar-time-zone (if calendar-time-zone calendar-time-zone 0))
|
|
(k (1- (/ m 3)))
|
|
(date (solar-equinoxes/solstices k y))
|
|
(s-hemi (and calendar-latitude (< calendar-latitude 0)))
|
|
(day (extract-calendar-day date))
|
|
(adj (solar-adj-time-for-dst
|
|
(list (extract-calendar-month date)
|
|
(truncate day)
|
|
(extract-calendar-year date))
|
|
(* 24 (- day (truncate day))))))
|
|
(list (list (car adj)
|
|
(format "%s %s"
|
|
(nth k (if s-hemi solar-s-hemi-seasons
|
|
solar-n-hemi-seasons))
|
|
(apply 'solar-time-string (cdr adj))))))))
|
|
|
|
(provide 'solar)
|
|
|
|
;;; solar.el ends here
|