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143 lines
4.7 KiB
EmacsLisp
143 lines
4.7 KiB
EmacsLisp
;;; time-date.el --- Date and time handling functions
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;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
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;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
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;; Masanobu Umeda <umerin@mse.kyutech.ac.jp>
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;; Keywords: mail news util
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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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;;; Code:
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(require 'parse-time)
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(autoload 'timezone-make-date-arpa-standard "timezone")
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;;;###autoload
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(defun date-to-time (date)
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"Convert DATE into time."
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(condition-case ()
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(apply 'encode-time
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(parse-time-string
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;; `parse-time-string' isn't sufficiently general or
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;; robust. It fails to grok some of the formats that
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;; timzeone does (e.g. dodgy post-2000 stuff from some
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;; Elms) and either fails or returns bogus values. Lars
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;; reverted this change, but that loses non-trivially
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;; often for me. -- fx
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(timezone-make-date-arpa-standard date)))
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(error (error "Invalid date: %s" date))))
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(defun time-to-seconds (time)
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"Convert TIME to a floating point number."
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(+ (* (car time) 65536.0)
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(cadr time)
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(/ (or (nth 2 time) 0) 1000000.0)))
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(defun seconds-to-time (seconds)
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"Convert SECONDS (a floating point number) to an Emacs time structure."
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(list (floor seconds 65536)
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(floor (mod seconds 65536))
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(floor (* (- seconds (ffloor seconds)) 1000000))))
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(defun time-less-p (t1 t2)
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"Say whether time T1 is less than time T2."
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(or (< (car t1) (car t2))
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(and (= (car t1) (car t2))
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(< (nth 1 t1) (nth 1 t2)))))
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(defun days-to-time (days)
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"Convert DAYS into time."
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(let* ((seconds (* 1.0 days 60 60 24))
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(rest (expt 2 16))
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(ms (condition-case nil (floor (/ seconds rest))
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(range-error (expt 2 16)))))
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(list ms (condition-case nil (round (- seconds (* ms rest)))
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(range-error (expt 2 16))))))
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(defun time-since (time)
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"Return the time since TIME, which is either an internal time or a date."
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(when (stringp time)
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;; Convert date strings to internal time.
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(setq time (date-to-time time)))
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(let* ((current (current-time))
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(rest (when (< (nth 1 current) (nth 1 time))
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(expt 2 16))))
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(list (- (+ (car current) (if rest -1 0)) (car time))
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(- (+ (or rest 0) (nth 1 current)) (nth 1 time)))))
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(defun subtract-time (t1 t2)
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"Subtract two internal times."
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(let ((borrow (< (cadr t1) (cadr t2))))
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(list (- (car t1) (car t2) (if borrow 1 0))
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(- (+ (if borrow 65536 0) (cadr t1)) (cadr t2)))))
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(defun date-to-day (date)
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"Return the number of days between year 1 and DATE."
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(time-to-days (date-to-time date)))
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(defun days-between (date1 date2)
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"Return the number of days between DATE1 and DATE2."
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(- (date-to-day date1) (date-to-day date2)))
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(defun date-leap-year-p (year)
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"Return t if YEAR is a leap year."
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(or (and (zerop (% year 4))
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(not (zerop (% year 100))))
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(zerop (% year 400))))
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(defun time-to-day-in-year (time)
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"Return the day number within the year of the date month/day/year."
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(let* ((tim (decode-time time))
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(month (nth 4 tim))
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(day (nth 3 tim))
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(year (nth 5 tim))
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(day-of-year (+ day (* 31 (1- month)))))
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(when (> month 2)
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(setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
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(when (date-leap-year-p year)
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(setq day-of-year (1+ day-of-year))))
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day-of-year))
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(defun time-to-days (time)
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"The number of days between the Gregorian date 0001-12-31bce and TIME.
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The Gregorian date Sunday, December 31, 1bce is imaginary."
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(let* ((tim (decode-time time))
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(month (nth 4 tim))
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(day (nth 3 tim))
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(year (nth 5 tim)))
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(+ (time-to-day-in-year time) ; Days this year
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(* 365 (1- year)) ; + Days in prior years
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(/ (1- year) 4) ; + Julian leap years
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(- (/ (1- year) 100)) ; - century years
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(/ (1- year) 400)))) ; + Gregorian leap years
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;;;###autoload
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(defun safe-date-to-time (date)
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"Parse DATE and return a time structure.
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If DATE is malformed, a zero time will be returned."
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(condition-case ()
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(date-to-time date)
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(error '(0 0))))
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(provide 'time-date)
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;;; time-date.el ends here
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