lisp/calendar/time-date.el

   1 ;;; time-date.el --- date and time handling functions
   2 ;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
   3
   4 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   5 ;;      Masanobu Umeda <umerin@mse.kyutech.ac.jp>
   6 ;; Keywords: mail news util
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;;; Code:
  28
  29 (require 'parse-time)
  30
  31 (autoload 'timezone-make-date-arpa-standard "timezone")
  32
  33 ;;;###autoload
  34 (defun date-to-time (date)
  35   "Parse a string that represents a date-time and return a time value."
  36   (condition-case ()
  37       (apply 'encode-time
  38              (parse-time-string
  39               ;; `parse-time-string' isn't sufficiently general or
  40               ;; robust.  It fails to grok some of the formats that
  41               ;; timzeone does (e.g. dodgy post-2000 stuff from some
  42               ;; Elms) and either fails or returns bogus values.  Lars
  43               ;; reverted this change, but that loses non-trivially
  44               ;; often for me.  -- fx
  45               (timezone-make-date-arpa-standard date)))
  46     (error (error "Invalid date: %s" date))))
  47
  48 (defun time-to-seconds (time)
  49   "Convert time value TIME to a floating point number.
  50 You can use `float-time' instead."
  51   (+ (* (car time) 65536.0)
  52      (cadr time)
  53      (/ (or (nth 2 time) 0) 1000000.0)))
  54
  55 ;;;###autoload
  56 (defun seconds-to-time (seconds)
  57   "Convert SECONDS (a floating point number) to a time value."
  58   (list (floor seconds 65536)
  59         (floor (mod seconds 65536))
  60         (floor (* (- seconds (ffloor seconds)) 1000000))))
  61
  62 ;;;###autoload
  63 (defun time-less-p (t1 t2)
  64   "Say whether time value T1 is less than time value T2."
  65   (or (< (car t1) (car t2))
  66       (and (= (car t1) (car t2))
  67            (< (nth 1 t1) (nth 1 t2)))))
  68
  69 ;;;###autoload
  70 (defun days-to-time (days)
  71   "Convert DAYS into a time value."
  72   (let* ((seconds (* 1.0 days 60 60 24))
  73          (rest (expt 2 16))
  74          (ms (condition-case nil (floor (/ seconds rest))
  75                (range-error (expt 2 16)))))
  76     (list ms (condition-case nil (round (- seconds (* ms rest)))
  77                (range-error (expt 2 16))))))
  78
  79 ;;;###autoload
  80 (defun time-since (time)
  81   "Return the time elapsed since TIME.
  82 TIME should be either a time value or a date-time string."
  83   (when (stringp time)
  84     ;; Convert date strings to internal time.
  85     (setq time (date-to-time time)))
  86   (let* ((current (current-time))
  87          (rest (when (< (nth 1 current) (nth 1 time))
  88                  (expt 2 16))))
  89     (list (- (+ (car current) (if rest -1 0)) (car time))
  90           (- (+ (or rest 0) (nth 1 current)) (nth 1 time)))))
  91
  92 ;;;###autoload
  93 (defalias 'subtract-time 'time-subtract)
  94
  95 ;;;###autoload
  96 (defun time-subtract (t1 t2)
  97   "Subtract two time values.
  98 Return the difference in the format of a time value."
  99   (let ((borrow (< (cadr t1) (cadr t2))))
 100     (list (- (car t1) (car t2) (if borrow 1 0))
 101           (- (+ (if borrow 65536 0) (cadr t1)) (cadr t2)))))
 102
 103 ;;;###autoload
 104 (defun time-add (t1 t2)
 105   "Add two time values.  One should represent a time difference."
 106   (let ((high (car t1))
 107         (low (if (consp (cdr t1)) (nth 1 t1) (cdr t1)))
 108         (micro (if (numberp (car-safe (cdr-safe (cdr t1))))
 109                    (nth 2 t1)
 110                  0))
 111         (high2 (car t2))
 112         (low2 (if (consp (cdr t2)) (nth 1 t2) (cdr t2)))
 113         (micro2 (if (numberp (car-safe (cdr-safe (cdr t2))))
 114                     (nth 2 t2)
 115                   0)))
 116     ;; Add
 117     (setq micro (+ micro micro2))
 118     (setq low (+ low low2))
 119     (setq high (+ high high2))
 120
 121     ;; Normalize
 122     ;; `/' rounds towards zero while `mod' returns a positive number,
 123     ;; so we can't rely on (= a (+ (* 100 (/ a 100)) (mod a 100))).
 124     (setq low (+ low (/ micro 1000000) (if (< micro 0) -1 0)))
 125     (setq micro (mod micro 1000000))
 126     (setq high (+ high (/ low 65536) (if (< low 0) -1 0)))
 127     (setq low (logand low 65535))
 128
 129     (list high low micro)))
 130
 131 ;;;###autoload
 132 (defun date-to-day (date)
 133   "Return the number of days between year 1 and DATE.
 134 DATE should be a date-time string."
 135   (time-to-days (date-to-time date)))
 136
 137 ;;;###autoload
 138 (defun days-between (date1 date2)
 139   "Return the number of days between DATE1 and DATE2.
 140 DATE1 and DATE2 should be date-time strings."
 141   (- (date-to-day date1) (date-to-day date2)))
 142
 143 ;;;###autoload
 144 (defun date-leap-year-p (year)
 145   "Return t if YEAR is a leap year."
 146   (or (and (zerop (% year 4))
 147            (not (zerop (% year 100))))
 148       (zerop (% year 400))))
 149
 150 ;;;###autoload
 151 (defun time-to-day-in-year (time)
 152   "Return the day number within the year of the date month/day/year."
 153   (let* ((tim (decode-time time))
 154          (month (nth 4 tim))
 155          (day (nth 3 tim))
 156          (year (nth 5 tim))
 157          (day-of-year (+ day (* 31 (1- month)))))
 158     (when (> month 2)
 159       (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
 160       (when (date-leap-year-p year)
 161         (setq day-of-year (1+ day-of-year))))
 162     day-of-year))
 163
 164 ;;;###autoload
 165 (defun time-to-days (time)
 166   "The number of days between the Gregorian date 0001-12-31bce and TIME.
 167 TIME should be a time value.
 168 The Gregorian date Sunday, December 31, 1bce is imaginary."
 169   (let* ((tim (decode-time time))
 170          (month (nth 4 tim))
 171          (day (nth 3 tim))
 172          (year (nth 5 tim)))
 173     (+ (time-to-day-in-year time)       ;       Days this year
 174        (* 365 (1- year))                ;       + Days in prior years
 175        (/ (1- year) 4)                  ;       + Julian leap years
 176        (- (/ (1- year) 100))            ;       - century years
 177        (/ (1- year) 400))))             ;       + Gregorian leap years
 178
 179 ;;;###autoload
 180 (defun safe-date-to-time (date)
 181   "Parse a string that represents a date-time and return a time value.
 182 If DATE is malformed, return a time value of zeros."
 183   (condition-case ()
 184       (date-to-time date)
 185     (error '(0 0))))
 186
 187 (provide 'time-date)
 188
 189 ;;; arch-tag: addcf07b-b20a-465b-af72-550b8ac5190f
 190 ;;; time-date.el ends here