* bug#20583: calendar-absolute-from-gregorian
@ 2015-05-15 4:20 Nicholas Strauss
2015-05-16 0:54 ` Glenn Morris
0 siblings, 1 reply; 5+ messages in thread
From: Nicholas Strauss @ 2015-05-15 4:20 UTC (permalink / raw)
To: 20583; +Cc: gjs
Hi Bug Emacs,
Why does (calendar-absolute-from-gregorian '(10 10 1582))
return 577731?
(calendar-generate '(10 1582)) is another example of this
error.
There are no Gregorian dates from 5 - 15 October 1582.
Pope Gregory declared this.
Hence, ALL absolute day numbers in calendar before 1582
are probably wrong. So using emacs for historical computations
is bogus.
I will work on writing calendar-absolute-from-gregorian and
calendar-gregorian-from-absolute to patch this error.
Let me know if this sounds OK.
nick
ncs@alum.mit.edu
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#20583: calendar-absolute-from-gregorian
2015-05-15 4:20 bug#20583: calendar-absolute-from-gregorian Nicholas Strauss
@ 2015-05-16 0:54 ` Glenn Morris
2015-05-16 1:48 ` Nicholas Strauss
0 siblings, 1 reply; 5+ messages in thread
From: Glenn Morris @ 2015-05-16 0:54 UTC (permalink / raw)
To: Nicholas Strauss; +Cc: 20583, gjs
Nicholas Strauss wrote:
> Why does (calendar-absolute-from-gregorian '(10 10 1582))
> return 577731?
> (calendar-generate '(10 1582)) is another example of this
> error.
It's behaving as designed. It's a utility function that operates on the
basis that today's calendar system is valid for all time. It's not meant
as literally historically accurate, and I think trying to make it so (by
introducing discontinuities at certain dates) would be a mistake. See eg
thread at:
http://lists.gnu.org/archive/html/emacs-devel/2006-07/msg01008.html
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#20583: calendar-absolute-from-gregorian
2015-05-16 0:54 ` Glenn Morris
@ 2015-05-16 1:48 ` Nicholas Strauss
2015-05-22 15:36 ` Nicholas Strauss
0 siblings, 1 reply; 5+ messages in thread
From: Nicholas Strauss @ 2015-05-16 1:48 UTC (permalink / raw)
To: Glenn Morris; +Cc: 20583, gjs
Hi Glenn,
The real point here is that Calendar Systems are instruments and as
subject are subject to error (Think like an engineer!). The real world
is messy -- Pope Gregory abolished some days, and various countries
took their time to jump on the band wagon.
I think what Reingold is/was trying to do was to use "absolute" as an
internal reference format -- a primary key -- that would correlate all the
other calendars.
there are other "absolute" choices for internal references.
Peter Duffett-Smith took a different approach -- he counts 2415020
days from January 1, 4713 BC until the 1900 epoch, January 0.5, 1900.
This crops up in sqlite3 calculations for date() and also common
javascript formulas.
I am still researching this.
If our civilization lasts for any appreciable time, having a consistent
calendar will be crucial for keeping a consistent history.
I think this helps why I am stressing the astronomy. If an Aztec calendar
records an eclipse on a certain day, that's pretty much it.
Nick
On Fri, May 15, 2015 at 5:54 PM, Glenn Morris <rgm@gnu.org> wrote:
> Nicholas Strauss wrote:
>
>> Why does (calendar-absolute-from-gregorian '(10 10 1582))
>> return 577731?
>> (calendar-generate '(10 1582)) is another example of this
>> error.
>
> It's behaving as designed. It's a utility function that operates on the
> basis that today's calendar system is valid for all time. It's not meant
> as literally historically accurate, and I think trying to make it so (by
> introducing discontinuities at certain dates) would be a mistake. See eg
> thread at:
>
> http://lists.gnu.org/archive/html/emacs-devel/2006-07/msg01008.html
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#20583: calendar-absolute-from-gregorian
2015-05-16 1:48 ` Nicholas Strauss
@ 2015-05-22 15:36 ` Nicholas Strauss
2015-05-24 15:29 ` Nicholas Strauss
0 siblings, 1 reply; 5+ messages in thread
From: Nicholas Strauss @ 2015-05-22 15:36 UTC (permalink / raw)
To: Glenn Morris; +Cc: 20583, gjs
[-- Attachment #1: Type: text/plain, Size: 551 bytes --]
There are other day number systems more common than the emacs
"absolute" day number --
the "astro" or Julian day number and the proleptic Gregorian system
used by sqlite3
e.g. select julianday("-4713-11-24").
cal-julian.el:alendar-astro-to-absolute refers to "astro".
Proleptic Gregorian day 0 = November 24, 4714 BC while "astro" day 0 =
January 1, 4713 BC.
I'm attaching julian.lisp which has calendar-correlate-from-date and
calendar-correlate-from-julianday
may help with days before 1582. These are based on Peter
Duffett-Smiths calculations.
[-- Attachment #2: julian.lisp --]
[-- Type: application/octet-stream, Size: 6192 bytes --]
;; julian.lisp Copyright 2015 Nicholas C. Strauss (ncs@alum.mit.edu)
;;
;; This program 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.
;;
;; This program 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 this program. If not, see <http://www.gnu.org/licenses/>
;;;###cal-autoload
(defun calendar-julianday-from-gregorian (date)
"Compute the Julian day corresponding to the date
calculated from Monday, Jan 1, 4713 BCE using
the Julian calendar until October 5, 1582 thence the
Gregorian calendar from October 15, 1582"
(let ((day (calendar-extract-day date))
(month (calendar-extract-month date))
(year (calendar-extract-year date)))
;; b=gregorian correction
;; c=elapsed years
;; d=elapsed months this year
(if (and (= year 1582) (= month 10)
(>= day 5)
(< day 15))
0.0e+NaN
(progn
(if (< year 1) (setq year (+ year 1)))
(if (< month 3) (progn
(setq year (+ year -1))
(setq month (+ month 12)))
)
(setq a (ffloor (/ year 100)))
(if (or (< year 1582)
(and (= year 1582) (< month 10))
(and (= year 1582) (= month 10) (< day 5)))
(setq b 0) ;; julian
(setq b (+ 2 (- a) ;; gregorian
(ffloor (/ a 4)))))
(if (< year 0)
(setq c (+ (ftruncate (+ (* 365.25 year) -0.75))
-694025))
(setq c (+ (ffloor (* 365.25 year))
-694025)))
(setq d (ffloor (* 30.6001 (+ month 1))))
(+ day b c d -0.5 2415020)
)
)
)
)
;;;###cal-autoload
(defun calendar-gregorian-from-julianday (julianday)
"Compute the date corresponding to the Julian day
calculated from Monday, Jan 1, 4713 BCE using
the Julian calendar until October 5, 1582 thence the
Gregorian calendar from October 15, 1582"
(cond
((isnan julianday)
julianday)
(t
(progn
(setq julianday (+ julianday -2415020))
(setq d (+ julianday 0.5))
(setq i (ffloor d))
(setq fd (+ d (- i)))
(if (< (abs (+ fd -1.0))
1.0e-10)
(progn
(setq fd 0.0)
(setq i (+ i 1)))
)
(if (> i -115860)
(progn
(setq a (+ (ffloor (+ (/ i 36524.25) 0.99835726))
14))
(setq i (+ i 1 a
(- (ffloor (/ a 4.0)))))
)
)
(setq b (ffloor (+ (/ i 365.25) 0.802601)))
(setq c (+ i (- (ffloor (+ (* 365.25 b)
0.750001)))
416))
(setq g (ffloor (/ c 30.6001)))
(setq day (ffloor (+ c
(- (ffloor (* 30.6001 g)))
fd)))
(if (> g 13.5)
(setq month (+ g -13))
(setq month (+ g -1)))
(if (> month 2.5)
(setq year (+ b 1899))
(setq year (+ b 1900)))
(if (< year 0)
(setq year (+ year -1)))
(setq julianday (+ julianday 2415020))
(setq b (* (ftruncate (/ (+ julianday 1.5) 7))
7))
(setq dayofweek (+ 1
(ftruncate (+ julianday 1.5 (- b)))
))
;; (list dayofweek
;; (* fd 24)
;; month
;; day
;; year))
(list month
day
year))
)
)
)
;;;###cal-autoload
(defun calendar-julianday-from-proleptic-gregorian (date)
"Compute the Julian day corresponding to the date
calculated from Monday, Jan 1, 4713 BCE using
the Julian calendar until October 5, 1582 thence the
Gregorian calendar from October 15, 1582"
(let ((day (calendar-extract-day date))
(month (calendar-extract-month date))
(year (calendar-extract-year date)))
;; b=gregorian correction
;; c=elapsed years
;; d=elapsed months this year
(if (and (= year 1582) (= month 10)
(>= day 5)
(< day 15))
0.0e+NaN
(progn
(if (< month 3) (progn
(setq year (+ year -1))
(setq month (+ month 12)))
)
(setq a (ffloor (/ year 100)))
(setq b (+ 2
(- a)
(ffloor (/ a 4))))
(if (< year 0)
(setq c (+ (ftruncate (+ (* 365.25 year) -0.75))
-694025))
(setq c (+ (ffloor (* 365.25 year))
-694025)))
(setq d (ffloor (* 30.6001 (+ month 1))))
(+ day b c d -0.5 2415020)
)
)
)
)
;;;###cal-autoload
(defun calendar-proleptic-gregorian-from-julianday (julianday)
"Compute the date corresponding to the Julian day
calculated from Monday, November 24, 4713 BCE using
the Gregorian calendar."
(cond
((isnan julianday)
julianday)
(t
(progn
(setq julianday (+ julianday -2415020))
(setq d (+ julianday 0.5))
(setq i (ffloor d))
(setq fd (+ d (- i)))
(if (< (abs (+ fd -1.0))
1.0e-10)
(progn
(setq fd 0.0)
(setq i (+ i 1)))
)
(setq a (+ (ffloor (+ (/ i 36524.25) 0.99835726))
14))
(setq i (+ i 1 a
(- (ffloor (/ a 4.0)))))
(setq b (ffloor (+ (/ i 365.25) 0.802601)))
(setq c (+ i (- (ffloor (+ (* 365.25 b)
0.750001)))
416))
(setq g (ffloor (/ c 30.6001)))
(setq day (ffloor (+ c
(- (ffloor (* 30.6001 g)))
fd)))
(if (> g 13.5)
(setq month (+ g -13))
(setq month (+ g -1)))
(if (> month 2.5)
(setq year (+ b 1899))
(setq year (+ b 1900)))
(setq julianday (+ julianday 2415020))
(setq b (* (ftruncate (/ (+ julianday 1.5) 7))
7))
(setq dayofweek (+ 1
(ftruncate (+ julianday 1.5 (- b)))
))
;; (list dayofweek
;; (* fd 24)
;; month
;; day
;; year))
(list month
day
year))
)
)
)
(defun calendar-correlate-from-julianday (julianday)
(let ((date-proleptic (calendar-proleptic-gregorian-from-julianday julianday))
(date-gregorian (calendar-gregorian-from-julianday julianday)))
(list date-proleptic date-gregorian))
)
(defun calendar-correlate-from-date (date)
(let ((jd-proleptic (calendar-julianday-from-proleptic-gregorian date))
(jd-gregorian (calendar-julianday-from-gregorian date)))
(list jd-proleptic jd-gregorian))
)
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#20583: calendar-absolute-from-gregorian
2015-05-22 15:36 ` Nicholas Strauss
@ 2015-05-24 15:29 ` Nicholas Strauss
0 siblings, 0 replies; 5+ messages in thread
From: Nicholas Strauss @ 2015-05-24 15:29 UTC (permalink / raw)
To: Glenn Morris; +Cc: 20583
[-- Attachment #1: Type: text/plain, Size: 784 bytes --]
Corrected comments to calendar-julianday-from-proleptic-gregorian
and cond for year 1582.
File requires calendar.el
Nick
On Fri, May 22, 2015 at 8:36 AM, Nicholas Strauss
<nicholas.strauss@gmail.com> wrote:
> There are other day number systems more common than the emacs
> "absolute" day number --
> the "astro" or Julian day number and the proleptic Gregorian system
> used by sqlite3
> e.g. select julianday("-4713-11-24").
> cal-julian.el:alendar-astro-to-absolute refers to "astro".
> Proleptic Gregorian day 0 = November 24, 4714 BC while "astro" day 0 =
> January 1, 4713 BC.
> I'm attaching julian.lisp which has calendar-correlate-from-date and
> calendar-correlate-from-julianday
> may help with days before 1582. These are based on Peter
> Duffett-Smiths calculations.
[-- Attachment #2: julian.lisp --]
[-- Type: application/octet-stream, Size: 5986 bytes --]
;; julian.lisp Copyright 2015 Nicholas C. Strauss (ncs@alum.mit.edu)
;;
;; This program 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.
;;
;; This program 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 this program. If not, see <http://www.gnu.org/licenses/>
;; requires calendar.el
;;;###cal-autoload
(defun calendar-julianday-from-gregorian (date)
"Compute the Julian day corresponding to the date
calculated from Monday, Jan 1, 4713 BCE using
the Julian calendar until October 5, 1582 thence the
Gregorian calendar from October 15, 1582"
(let ((day (calendar-extract-day date))
(month (calendar-extract-month date))
(year (calendar-extract-year date)))
;; b=gregorian correction
;; c=elapsed years
;; d=elapsed months this year
(if (and (= year 1582) (= month 10)
(>= day 5)
(< day 15))
0.0e+NaN
(progn
(if (< year 1) (setq year (+ year 1)))
(if (< month 3) (progn
(setq year (+ year -1))
(setq month (+ month 12)))
)
(setq a (ffloor (/ year 100)))
(if (or (< year 1582)
(and (= year 1582) (< month 10))
(and (= year 1582) (= month 10) (< day 5)))
(setq b 0) ;; julian
(setq b (+ 2 (- a) ;; gregorian
(ffloor (/ a 4)))))
(if (< year 0)
(setq c (+ (ftruncate (+ (* 365.25 year) -0.75))
-694025))
(setq c (+ (ffloor (* 365.25 year))
-694025)))
(setq d (ffloor (* 30.6001 (+ month 1))))
(+ day b c d -0.5 2415020)
)
)
)
)
;;;###cal-autoload
(defun calendar-gregorian-from-julianday (julianday)
"Compute the date corresponding to the Julian day
calculated from Monday, Jan 1, 4713 BCE using
the Julian calendar until October 5, 1582 thence the
Gregorian calendar from October 15, 1582"
(cond
((isnan julianday)
julianday)
(t
(progn
(setq julianday (+ julianday -2415020))
(setq d (+ julianday 0.5))
(setq i (ffloor d))
(setq fd (+ d (- i)))
(if (< (abs (+ fd -1.0))
1.0e-10)
(progn
(setq fd 0.0)
(setq i (+ i 1)))
)
(if (> i -115860)
(progn
(setq a (+ (ffloor (+ (/ i 36524.25) 0.99835726))
14))
(setq i (+ i 1 a
(- (ffloor (/ a 4.0)))))
)
)
(setq b (ffloor (+ (/ i 365.25) 0.802601)))
(setq c (+ i (- (ffloor (+ (* 365.25 b)
0.750001)))
416))
(setq g (ffloor (/ c 30.6001)))
(setq day (ffloor (+ c
(- (ffloor (* 30.6001 g)))
fd)))
(if (> g 13.5)
(setq month (+ g -13))
(setq month (+ g -1)))
(if (> month 2.5)
(setq year (+ b 1899))
(setq year (+ b 1900)))
(if (< year 0)
(setq year (+ year -1)))
(setq julianday (+ julianday 2415020))
(setq b (* (ftruncate (/ (+ julianday 1.5) 7))
7))
(setq dayofweek (+ 1
(ftruncate (+ julianday 1.5 (- b)))
))
;; (list dayofweek
;; (* fd 24)
;; month
;; day
;; year))
(list month
day
year))
)
)
)
;;;###cal-autoload
(defun calendar-julianday-from-proleptic-gregorian (date)
"Compute the julian day corresponding to the date
calculated from Monday, November 24, 4713 BCE using
the Gregorian calendar."
(let ((day (calendar-extract-day date))
(month (calendar-extract-month date))
(year (calendar-extract-year date)))
(progn
(if (< month 3) (progn
(setq year (+ year -1))
(setq month (+ month 12)))
)
(setq a (ffloor (/ year 100)))
(setq b (+ 2
(- a)
(ffloor (/ a 4))))
(if (< year 0)
(setq c (+ (ftruncate (+ (* 365.25 year) -0.75))
-694025))
(setq c (+ (ffloor (* 365.25 year))
-694025)))
(setq d (ffloor (* 30.6001 (+ month 1))))
(+ day b c d -0.5 2415020)
)
)
)
;;;###cal-autoload
(defun calendar-proleptic-gregorian-from-julianday (julianday)
"Compute the date corresponding to the Julian day
calculated from Monday, November 24, 4713 BCE using
the Gregorian calendar."
(cond
((isnan julianday)
julianday)
(t
(progn
(setq julianday (+ julianday -2415020))
(setq d (+ julianday 0.5))
(setq i (ffloor d))
(setq fd (+ d (- i)))
(if (< (abs (+ fd -1.0))
1.0e-10)
(progn
(setq fd 0.0)
(setq i (+ i 1)))
)
(setq a (+ (ffloor (+ (/ i 36524.25) 0.99835726))
14))
(setq i (+ i 1 a
(- (ffloor (/ a 4.0)))))
(setq b (ffloor (+ (/ i 365.25) 0.802601)))
(setq c (+ i (- (ffloor (+ (* 365.25 b)
0.750001)))
416))
(setq g (ffloor (/ c 30.6001)))
(setq day (ffloor (+ c
(- (ffloor (* 30.6001 g)))
fd)))
(if (> g 13.5)
(setq month (+ g -13))
(setq month (+ g -1)))
(if (> month 2.5)
(setq year (+ b 1899))
(setq year (+ b 1900)))
(setq julianday (+ julianday 2415020))
(setq b (* (ftruncate (/ (+ julianday 1.5) 7))
7))
(setq dayofweek (+ 1
(ftruncate (+ julianday 1.5 (- b)))
))
;; (list dayofweek
;; (* fd 24)
;; month
;; day
;; year))
(list month
day
year))
)
)
)
(defun calendar-correlate-from-julianday (julianday)
(let ((date-proleptic (calendar-proleptic-gregorian-from-julianday julianday))
(date-gregorian (calendar-gregorian-from-julianday julianday)))
(list date-proleptic date-gregorian))
)
(defun calendar-correlate-from-date (date)
(let ((jd-proleptic (calendar-julianday-from-proleptic-gregorian date))
(jd-gregorian (calendar-julianday-from-gregorian date)))
(list jd-proleptic jd-gregorian))
)
^ permalink raw reply [flat|nested] 5+ messages in thread
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-- links below jump to the message on this page --
2015-05-15 4:20 bug#20583: calendar-absolute-from-gregorian Nicholas Strauss
2015-05-16 0:54 ` Glenn Morris
2015-05-16 1:48 ` Nicholas Strauss
2015-05-22 15:36 ` Nicholas Strauss
2015-05-24 15:29 ` Nicholas Strauss
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