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emacs/lisp/timezone.el
Paul Eggert db853edc0b (timezone-time-from-absolute): Fix off-by-one 
error in current-time-origin.
1996-10-28 03:55:59 +00:00

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;;; timezone.el --- time zone package for GNU Emacs
;; Copyright (C) 1990, 1991, 1992, 1993, 1996 Free Software Foundation, Inc.
;; Author: Masanobu Umeda
;; Maintainer: umerin@mse.kyutech.ac.jp
;; Keywords: news
;; 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.
;;; Code:
(provide 'timezone)
(defvar timezone-world-timezones
'(("PST" . -800)
("PDT" . -700)
("MST" . -700)
("MDT" . -600)
("CST" . -600)
("CDT" . -500)
("EST" . -500)
("EDT" . -400)
("AST" . -400) ;by <clamen@CS.CMU.EDU>
("NST" . -330) ;by <clamen@CS.CMU.EDU>
("UT" . +000)
("GMT" . +000)
("BST" . +100)
("MET" . +100)
("EET" . +200)
("JST" . +900)
("GMT+1" . +100) ("GMT+2" . +200) ("GMT+3" . +300)
("GMT+4" . +400) ("GMT+5" . +500) ("GMT+6" . +600)
("GMT+7" . +700) ("GMT+8" . +800) ("GMT+9" . +900)
("GMT+10" . +1000) ("GMT+11" . +1100) ("GMT+12" . +1200) ("GMT+13" . +1300)
("GMT-1" . -100) ("GMT-2" . -200) ("GMT-3" . -300)
("GMT-4" . -400) ("GMT-5" . -500) ("GMT-6" . -600)
("GMT-7" . -700) ("GMT-8" . -800) ("GMT-9" . -900)
("GMT-10" . -1000) ("GMT-11" . -1100) ("GMT-12" . -1200))
"*Time differentials of timezone from GMT in +-HHMM form.
This list is obsolescent, and is present only for backwards compatibility,
because time zone names are ambiguous in practice.
Use `current-time-zone' instead.")
(defvar timezone-months-assoc
'(("JAN" . 1)("FEB" . 2)("MAR" . 3)
("APR" . 4)("MAY" . 5)("JUN" . 6)
("JUL" . 7)("AUG" . 8)("SEP" . 9)
("OCT" . 10)("NOV" . 11)("DEC" . 12))
"Alist of first three letters of a month and its numerical representation.")
(defun timezone-make-date-arpa-standard (date &optional local timezone)
"Convert DATE to an arpanet standard date.
Optional 1st argument LOCAL specifies the default local timezone of the DATE;
if nil, GMT is assumed.
Optional 2nd argument TIMEZONE specifies a time zone to be represented in;
if nil, the local time zone is assumed."
(let ((new (timezone-fix-time date local timezone)))
(timezone-make-arpa-date (aref new 0) (aref new 1) (aref new 2)
(timezone-make-time-string
(aref new 3) (aref new 4) (aref new 5))
(aref new 6))
))
(defun timezone-make-date-sortable (date &optional local timezone)
"Convert DATE to a sortable date string.
Optional 1st argument LOCAL specifies the default local timezone of the DATE;
if nil, GMT is assumed.
Optional 2nd argument TIMEZONE specifies a timezone to be represented in;
if nil, the local time zone is assumed."
(let ((new (timezone-fix-time date local timezone)))
(timezone-make-sortable-date (aref new 0) (aref new 1) (aref new 2)
(timezone-make-time-string
(aref new 3) (aref new 4) (aref new 5)))
))
;;
;; Parsers and Constructors of Date and Time
;;
(defun timezone-make-arpa-date (year month day time &optional timezone)
"Make arpanet standard date string from YEAR, MONTH, DAY, and TIME.
Optional argument TIMEZONE specifies a time zone."
(let ((zone
(if (listp timezone)
(let* ((m (timezone-zone-to-minute timezone))
(absm (if (< m 0) (- m) m)))
(format "%c%02d%02d"
(if (< m 0) ?- ?+) (/ absm 60) (% absm 60)))
timezone)))
(format "%02d %s %04d %s %s"
day
(capitalize (car (rassq month timezone-months-assoc)))
year
time
zone)))
(defun timezone-make-sortable-date (year month day time)
"Make sortable date string from YEAR, MONTH, DAY, and TIME."
(format "%4d%02d%02d%s"
year month day time))
(defun timezone-make-time-string (hour minute second)
"Make time string from HOUR, MINUTE, and SECOND."
(format "%02d:%02d:%02d" hour minute second))
(defun timezone-parse-date (date)
"Parse DATE and return a vector [YEAR MONTH DAY TIME TIMEZONE].
19 is prepended to year if necessary. Timezone may be nil if nothing.
Understands the following styles:
(1) 14 Apr 89 03:20[:12] [GMT]
(2) Fri, 17 Mar 89 4:01[:33] [GMT]
(3) Mon Jan 16 16:12[:37] [GMT] 1989
(4) 6 May 1992 1641-JST (Wednesday)
(5) 22-AUG-1993 10:59:12.82
(6) Thu, 11 Apr 16:17:12 91 [MET]
(7) Mon, 6 Jul 16:47:20 T 1992 [MET]
(8) 1996-06-24 21:13:12 [GMT]"
;; Get rid of any text properties.
(and (stringp date)
(or (text-properties-at 0 date)
(next-property-change 0 date))
(setq date (copy-sequence date))
(set-text-properties 0 (length date) nil date))
(let ((date (or date ""))
(year nil)
(month nil)
(day nil)
(time nil)
(zone nil)) ;This may be nil.
(cond ((string-match
"\\([^ \t,]+\\),[ \t]+\\([0-9]+\\)[ \t]+\\([^ \t,]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]+\\(T[ \t]+\\|\\)\\([0-9]+\\)[ \t]*\\'" date)
;; Styles: (6) and (7) without timezone
(setq year 6 month 3 day 2 time 4 zone nil))
((string-match
"\\([^ \t,]+\\),[ \t]+\\([0-9]+\\)[ \t]+\\([^ \t,]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]+\\(T[ \t]+\\|\\)\\([0-9]+\\)[ \t]*\\([-+a-zA-Z0-9]+\\)" date)
;; Styles: (6) and (7) with timezone and buggy timezone
(setq year 6 month 3 day 2 time 4 zone 7))
((string-match
"\\([0-9]+\\)[ \t]+\\([^ \t,]+\\)[ \t]+\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]*\\'" date)
;; Styles: (1) and (2) without timezone
(setq year 3 month 2 day 1 time 4 zone nil))
((string-match
"\\([0-9]+\\)[ \t]+\\([^ \t,]+\\)[ \t]+\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]*\\([-+a-zA-Z0-9]+\\)" date)
;; Styles: (1) and (2) with timezone and buggy timezone
(setq year 3 month 2 day 1 time 4 zone 5))
((string-match
"\\([^ \t,]+\\)[ \t]+\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]+\\([0-9]+\\)" date)
;; Styles: (3) without timezone
(setq year 4 month 1 day 2 time 3 zone nil))
((string-match
"\\([^ \t,]+\\)[ \t]+\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9:]+\\)[ \t]+\\([-+a-zA-Z0-9]+\\)[ \t]+\\([0-9]+\\)" date)
;; Styles: (3) with timezone
(setq year 5 month 1 day 2 time 3 zone 4))
((string-match
"\\([0-9]+\\)[ \t]+\\([^ \t,]+\\)[ \t]+\\([0-9]+\\)[ \t]+\\([0-9]+\\)[ \t]*\\([-+a-zA-Z0-9]+\\)" date)
;; Styles: (4) with timezone
(setq year 3 month 2 day 1 time 4 zone 5))
((string-match
"\\([0-9]+\\)-\\([A-Za-z]+\\)-\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9]+:[0-9]+\\)\\.[0-9]+" date)
;; Styles: (5) without timezone.
(setq year 3 month 2 day 1 time 4 zone nil))
((string-match
"\\([0-9]+\\)-\\([0-9]+\\)-\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9]+:[0-9]+\\)[ \t]*\\([-+a-zA-Z0-9]+\\)" date)
;; Styles: (8) with timezone.
(setq year 1 month 2 day 3 time 4 zone 5))
((string-match
"\\([0-9]+\\)-\\([0-9]+\\)-\\([0-9]+\\)[ \t]+\\([0-9]+:[0-9]+:[0-9]+\\)" date)
;; Styles: (8) without timezone.
(setq year 1 month 2 day 3 time 4 zone nil))
)
(if year
(progn
(setq year
(substring date (match-beginning year) (match-end year)))
;; It is now Dec 1992. 8 years before the end of the World.
(if (< (length year) 4)
(setq year (concat "19" (substring year -2 nil))))
(setq month
(if (= (aref date (+ (match-beginning month) 2)) ?-)
;; Handle numeric months, spanning exactly two digits.
(substring date
(match-beginning month)
(+ (match-beginning month) 2))
(let ((string (substring date
(match-beginning month)
(+ (match-beginning month) 3))))
(int-to-string
(cdr (assoc (upcase string) timezone-months-assoc))))))
(setq day
(substring date (match-beginning day) (match-end day)))
(setq time
(substring date (match-beginning time) (match-end time)))))
(if zone
(setq zone
(substring date (match-beginning zone) (match-end zone))))
;; Return a vector.
(if year
(vector year month day time zone)
(vector "0" "0" "0" "0" nil))
))
(defun timezone-parse-time (time)
"Parse TIME (HH:MM:SS) and return a vector [hour minute second].
Recognize HH:MM:SS, HH:MM, HHMMSS, HHMM."
(let ((time (or time ""))
(hour nil)
(minute nil)
(second nil))
(cond ((string-match "\\`\\([0-9]+\\):\\([0-9]+\\):\\([0-9]+\\)\\'" time)
;; HH:MM:SS
(setq hour 1 minute 2 second 3))
((string-match "\\`\\([0-9]+\\):\\([0-9]+\\)\\'" time)
;; HH:MM
(setq hour 1 minute 2 second nil))
((string-match "\\`\\([0-9][0-9]\\)\\([0-9][0-9]\\)\\([0-9][0-9]\\)\\'" time)
;; HHMMSS
(setq hour 1 minute 2 second 3))
((string-match "\\`\\([0-9][0-9]\\)\\([0-9][0-9]\\)\\'" time)
;; HHMM
(setq hour 1 minute 2 second nil))
)
;; Return [hour minute second]
(vector
(if hour
(substring time (match-beginning hour) (match-end hour)) "0")
(if minute
(substring time (match-beginning minute) (match-end minute)) "0")
(if second
(substring time (match-beginning second) (match-end second)) "0"))
))
;; Miscellaneous
(defun timezone-zone-to-minute (timezone)
"Translate TIMEZONE to an integer minute offset from GMT.
TIMEZONE can be a cons cell containing the output of current-time-zone,
or an integer of the form +-HHMM, or a time zone name."
(cond
((consp timezone)
(/ (car timezone) 60))
(timezone
(progn
(setq timezone
(or (cdr (assoc (upcase timezone) timezone-world-timezones))
;; +900
timezone))
(if (stringp timezone)
(setq timezone (string-to-int timezone)))
;; Taking account of minute in timezone.
;; HHMM -> MM
(let* ((abszone (abs timezone))
(minutes (+ (* 60 (/ abszone 100)) (% abszone 100))))
(if (< timezone 0) (- minutes) minutes))))
(t 0)))
(defun timezone-time-from-absolute (date seconds)
"Compute the UTC time equivalent to DATE at time SECONDS after midnight.
Return a list suitable as an argument to current-time-zone,
or nil if the date cannot be thus represented.
DATE is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC."
(let* ((current-time-origin 719163)
;; (timezone-absolute-from-gregorian 1 1 1970)
(days (- date current-time-origin))
(seconds-per-day (float 86400))
(seconds (+ seconds (* days seconds-per-day)))
(current-time-arithmetic-base (float 65536))
(hi (floor (/ seconds current-time-arithmetic-base)))
(hibase (* hi current-time-arithmetic-base))
(lo (floor (- seconds hibase))))
(and (< (abs (- seconds (+ hibase lo))) 2) ;; Check for integer overflow.
(cons hi lo))))
(defun timezone-time-zone-from-absolute (date seconds)
"Compute the local time zone for DATE at time SECONDS after midnight.
Return a list in the same format as current-time-zone's result,
or nil if the local time zone could not be computed.
DATE is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC."
(and (fboundp 'current-time-zone)
(let ((utc-time (timezone-time-from-absolute date seconds)))
(and utc-time
(let ((zone (current-time-zone utc-time)))
(and (car zone) zone))))))
(defun timezone-fix-time (date local timezone)
"Convert DATE (default timezone LOCAL) to YYYY-MM-DD-HH-MM-SS-ZONE vector.
If LOCAL is nil, it is assumed to be GMT.
If TIMEZONE is nil, use the local time zone."
(let* ((date (timezone-parse-date date))
(year (string-to-int (aref date 0)))
(year (cond ((< year 50)
(+ year 2000))
((< year 100)
(+ year 1900))
(t year)))
(month (string-to-int (aref date 1)))
(day (string-to-int (aref date 2)))
(time (timezone-parse-time (aref date 3)))
(hour (string-to-int (aref time 0)))
(minute (string-to-int (aref time 1)))
(second (string-to-int (aref time 2)))
(local (or (aref date 4) local)) ;Use original if defined
(timezone
(or timezone
(timezone-time-zone-from-absolute
(timezone-absolute-from-gregorian month day year)
(+ second (* 60 (+ minute (* 60 hour)))))))
(diff (- (timezone-zone-to-minute timezone)
(timezone-zone-to-minute local)))
(minute (+ minute diff))
(hour-fix (floor minute 60)))
(setq hour (+ hour hour-fix))
(setq minute (- minute (* 60 hour-fix)))
;; HOUR may be larger than 24 or smaller than 0.
(cond ((<= 24 hour) ;24 -> 00
(setq hour (- hour 24))
(setq day (1+ day))
(if (< (timezone-last-day-of-month month year) day)
(progn
(setq month (1+ month))
(setq day 1)
(if (< 12 month)
(progn
(setq month 1)
(setq year (1+ year))
))
)))
((> 0 hour)
(setq hour (+ hour 24))
(setq day (1- day))
(if (> 1 day)
(progn
(setq month (1- month))
(if (> 1 month)
(progn
(setq month 12)
(setq year (1- year))
))
(setq day (timezone-last-day-of-month month year))
)))
)
(vector year month day hour minute second timezone)))
;; Partly copied from Calendar program by Edward M. Reingold.
;; Thanks a lot.
(defun timezone-last-day-of-month (month year)
"The last day in MONTH during YEAR."
(if (and (= month 2) (timezone-leap-year-p year))
29
(aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))
(defun timezone-leap-year-p (year)
"Returns t if YEAR is a Gregorian leap year."
(or (and (zerop (% year 4))
(not (zerop (% year 100))))
(zerop (% year 400))))
(defun timezone-day-number (month day year)
"Return the day number within the year of the date month/day/year."
(let ((day-of-year (+ day (* 31 (1- month)))))
(if (> month 2)
(progn
(setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
(if (timezone-leap-year-p year)
(setq day-of-year (1+ day-of-year)))))
day-of-year))
(defun timezone-absolute-from-gregorian (month day year)
"The number of days between the Gregorian date 12/31/1 BC and month/day/year.
The Gregorian date Sunday, December 31, 1 BC is imaginary."
(+ (timezone-day-number month day year);; Days this year
(* 365 (1- year));; + Days in prior years
(/ (1- year) 4);; + Julian leap years
(- (/ (1- year) 100));; - century years
(/ (1- year) 400)));; + Gregorian leap years
;;; timezone.el ends here
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