1 ;;; time-date.el --- Date and time handling functions
2 ;; Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
4 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
5 ;; Masanobu Umeda <umerin@mse.kyutech.ac.jp>
6 ;; Keywords: mail news util
8 ;; This file is part of GNU Emacs.
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)
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.
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.
29 (eval-when-compile (require 'cl))
33 (autoload 'timezone-make-date-arpa-standard "timezone")
36 (defun date-to-time (date)
37 "Parse a string that represents a date-time and return a time value."
41 ;; `parse-time-string' isn't sufficiently general or
42 ;; robust. It fails to grok some of the formats that
43 ;; timezone does (e.g. dodgy post-2000 stuff from some
44 ;; Elms) and either fails or returns bogus values. Lars
45 ;; reverted this change, but that loses non-trivially
46 ;; often for me. -- fx
47 (timezone-make-date-arpa-standard date)))
48 (error (error "Invalid date: %s" date))))
50 (defun time-to-seconds (time)
51 "Convert time value TIME to a floating point number.
52 You can use `float-time' instead."
53 (+ (* (car time) 65536.0)
55 (/ (or (nth 2 time) 0) 1000000.0)))
58 (defun seconds-to-time (seconds)
59 "Convert SECONDS (a floating point number) to a time value."
60 (list (floor seconds 65536)
61 (floor (mod seconds 65536))
62 (floor (* (- seconds (ffloor seconds)) 1000000))))
65 (defun time-less-p (t1 t2)
66 "Say whether time value T1 is less than time value T2."
67 (or (< (car t1) (car t2))
68 (and (= (car t1) (car t2))
69 (< (nth 1 t1) (nth 1 t2)))))
72 (defun days-to-time (days)
73 "Convert DAYS into a time value."
74 (let* ((seconds (* 1.0 days 60 60 24))
76 (ms (condition-case nil (floor (/ seconds rest))
77 (range-error (expt 2 16)))))
78 (list ms (condition-case nil (round (- seconds (* ms rest)))
79 (range-error (expt 2 16))))))
82 (defun time-since (time)
83 "Return the time elapsed since TIME.
84 TIME should be either a time value or a date-time string."
86 ;; Convert date strings to internal time.
87 (setq time (date-to-time time)))
88 (let* ((current (current-time))
89 (rest (when (< (nth 1 current) (nth 1 time))
91 (list (- (+ (car current) (if rest -1 0)) (car time))
92 (- (+ (or rest 0) (nth 1 current)) (nth 1 time)))))
95 (defalias 'subtract-time 'time-subtract)
98 (defun time-subtract (t1 t2)
99 "Subtract two time values.
100 Return the difference in the format of a time value."
101 (let ((borrow (< (cadr t1) (cadr t2))))
102 (list (- (car t1) (car t2) (if borrow 1 0))
103 (- (+ (if borrow 65536 0) (cadr t1)) (cadr t2)))))
106 (defun time-add (t1 t2)
107 "Add two time values. One should represent a time difference."
108 (let ((high (car t1))
109 (low (if (consp (cdr t1)) (nth 1 t1) (cdr t1)))
110 (micro (if (numberp (car-safe (cdr-safe (cdr t1))))
114 (low2 (if (consp (cdr t2)) (nth 1 t2) (cdr t2)))
115 (micro2 (if (numberp (car-safe (cdr-safe (cdr t2))))
119 (setq micro (+ micro micro2))
120 (setq low (+ low low2))
121 (setq high (+ high high2))
124 ;; `/' rounds towards zero while `mod' returns a positive number,
125 ;; so we can't rely on (= a (+ (* 100 (/ a 100)) (mod a 100))).
126 (setq low (+ low (/ micro 1000000) (if (< micro 0) -1 0)))
127 (setq micro (mod micro 1000000))
128 (setq high (+ high (/ low 65536) (if (< low 0) -1 0)))
129 (setq low (logand low 65535))
131 (list high low micro)))
134 (defun date-to-day (date)
135 "Return the number of days between year 1 and DATE.
136 DATE should be a date-time string."
137 (time-to-days (date-to-time date)))
140 (defun days-between (date1 date2)
141 "Return the number of days between DATE1 and DATE2.
142 DATE1 and DATE2 should be date-time strings."
143 (- (date-to-day date1) (date-to-day date2)))
146 (defun date-leap-year-p (year)
147 "Return t if YEAR is a leap year."
148 (or (and (zerop (% year 4))
149 (not (zerop (% year 100))))
150 (zerop (% year 400))))
153 (defun time-to-day-in-year (time)
154 "Return the day number within the year of the date month/day/year."
155 (let* ((tim (decode-time time))
159 (day-of-year (+ day (* 31 (1- month)))))
161 (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
162 (when (date-leap-year-p year)
163 (setq day-of-year (1+ day-of-year))))
167 (defun time-to-days (time)
168 "The number of days between the Gregorian date 0001-12-31bce and TIME.
169 TIME should be a time value.
170 The Gregorian date Sunday, December 31, 1bce is imaginary."
171 (let* ((tim (decode-time time))
175 (+ (time-to-day-in-year time) ; Days this year
176 (* 365 (1- year)) ; + Days in prior years
177 (/ (1- year) 4) ; + Julian leap years
178 (- (/ (1- year) 100)) ; - century years
179 (/ (1- year) 400)))) ; + Gregorian leap years
181 (defun time-to-number-of-days (time)
182 "Return the number of days represented by TIME.
183 The number of days will be returned as a floating point number."
184 (/ (+ (* 1.0 65536 (car time)) (cadr time)) (* 60 60 24)))
187 (defun safe-date-to-time (date)
188 "Parse a string that represents a date-time and return a time value.
189 If DATE is malformed, return a time value of zeros."
196 ;;; time-date.el ends here