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emacs/lisp/timezone.el
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;;; timezone.el --- time zone package for GNU Emacs -*- lexical-binding: t -*-
;; Copyright (C) 1990-1993, 1996, 1999, 2001-2024 Free Software
;; Foundation, Inc.
;; Author: Masanobu Umeda <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 3 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
(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 2nd argument LOCAL specifies the default local timezone of the DATE;
if nil, GMT is assumed.
Optional 3rd 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 2nd argument LOCAL specifies the default local timezone of the DATE;
if nil, GMT is assumed.
Optional 3rd 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)
(format-time-string "%z" 0 (or timezone 0))
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].
Two-digit dates are `windowed'. Those <69 have 2000 added; otherwise 1900
is added. Three-digit dates have 1900 added.
TIMEZONE is nil for DATEs without a zone field.
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]
(9) 1996-06-24 21:13-ZONE
(10) 19960624T211312"
;; 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
"\\([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
;; This is most common in mail and news,
;; so it is worth trying first.
(setq year 3 month 2 day 1 time 4 zone 5))
((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
"\\([^ \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
"\\([^ \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]+\\)?[ \t]+\\([-+a-zA-Z0-9]+\\)" date)
;; Styles: (5) with timezone.
(setq year 3 month 2 day 1 time 4 zone 6))
((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]\\{4\\}\\)-?\\([0-9]\\{0,2\\}\\)-?\\([0-9]\\{0,2\\}\\)[T \t]+\\([0-9]\\{0,2\\}:?[0-9]\\{0,2\\}:?[0-9]\\{0,2\\}\\)[ \t]*\\([-+a-zA-Z]+[0-9:]*\\)" date)
;; Styles: (8) with timezone with a colon in it.
(setq year 1 month 2 day 3 time 4 zone 5))
((string-match
"\\([0-9]\\{4\\}\\)-?\\([0-9]\\{0,2\\}\\)-?\\([0-9]\\{0,2\\}\\)[T \t]+\\([0-9]+:?[0-9]+:?[0-9]+\\)" date)
;; Styles: (8) without timezone.
(setq year 1 month 2 day 3 time 4 zone nil))
)
(when year
(setq year (match-string year date))
;; Guess ambiguous years. Assume years < 69 don't predate the
;; Unix Epoch, so are 2000+. Three-digit years are assumed to
;; be relative to 1900.
(when (< (length year) 4)
(let ((y (string-to-number year)))
(when (< y 69)
(setq y (+ y 100)))
(setq year (int-to-string (+ 1900 y)))))
(setq month
(if (or (= (aref date (+ (match-beginning month) 2)) ?-)
(let ((n (string-to-number
(char-to-string
(aref date (+ (match-beginning month) 2))))))
(= (aref (number-to-string n) 0)
(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)))
(monthnum
(cdr (assoc (upcase string) timezone-months-assoc))))
(when monthnum
(int-to-string monthnum)))))
(setq day (match-string day date))
(setq time (match-string time date)))
(when zone (setq zone (match-string zone date)))
;; Return a vector.
(if (and year month)
(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 minute second)
(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 (match-string hour time) "0")
(if minute (match-string minute time) "0")
(if second (match-string second time) "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-number 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 Lisp timestamp 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 86400)
(day-seconds (* days seconds-per-day)))
(condition-case nil (time-add day-seconds seconds)
(range-error))))
(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."
(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-number (aref date 0)))
(year (cond ((< year 69)
(+ year 2000))
((< year 100)
(+ year 1900))
((< year 1000) ; possible 3-digit years.
(+ year 1900))
(t year)))
(month (string-to-number (aref date 1)))
(day (string-to-number (aref date 2)))
(time (timezone-parse-time (aref date 3)))
(hour (string-to-number (aref time 0)))
(minute (string-to-number (aref time 1)))
(second (string-to-number (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))
(when (< (timezone-last-day-of-month month year) day)
(setq month (1+ month))
(setq day 1)
(when (< 12 month)
(setq month 1)
(setq year (1+ year)))))
((> 0 hour)
(setq hour (+ hour 24))
(setq day (1- day))
(when (> 1 day)
(setq month (1- month))
(when (> 1 month)
(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)
"Return 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
(provide 'timezone)
;;; timezone.el ends here
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