1 ;;; time-date.el --- Date and time handling functions
2 ;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2005
3 ;; Free Software Foundation, Inc.
5 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
6 ;; Masanobu Umeda <umerin@mse.kyutech.ac.jp>
7 ;; Keywords: mail news util
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation; either version 2, or (at your option)
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs; see the file COPYING. If not, write to the
23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24 ;; Boston, MA 02110-1301, USA.
28 ;; Time values come in three formats. The oldest format is a cons
29 ;; cell of the form (HIGH . LOW). This format is obsolete, but still
30 ;; supported. The two other formats are the lists (HIGH LOW) and
31 ;; (HIGH LOW MICRO). The first two formats specify HIGH * 2^16 + LOW
32 ;; seconds; the third format specifies HIGH * 2^16 + LOW + MICRO /
33 ;; 1000000 seconds. We should have 0 <= MICRO < 1000000 and 0 <= LOW
34 ;; < 2^16. If the time value represents a point in time, then HIGH is
35 ;; nonnegative. If the time value is a time difference, then HIGH can
36 ;; be negative as well. The macro `with-decoded-time-value' and the
37 ;; function `encode-time-value' make it easier to deal with these
38 ;; three formats. See `time-subtract' for an example of how to use
43 (eval-when-compile (require 'cl))
45 (defmacro with-decoded-time-value (varlist &rest body)
46 "Decode a time value and bind it according to VARLIST, then eval BODY.
48 The value of the last form in BODY is returned.
50 Each element of the list VARLIST is a list of the form
51 \(HIGH-SYMBOL LOW-SYMBOL MICRO-SYMBOL [TYPE-SYMBOL] TIME-VALUE).
52 The time value TIME-VALUE is decoded and the result it bound to
53 the symbols HIGH-SYMBOL, LOW-SYMBOL and MICRO-SYMBOL.
55 The optional TYPE-SYMBOL is bound to the type of the time value.
56 Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH
57 LOW), and type 3 is the list (HIGH LOW MICRO)."
59 (debug ((&rest (symbolp symbolp symbolp &or [symbolp form] form))
62 (let* ((elt (pop varlist))
66 (type (unless (eq (length elt) 1)
68 (time-value (car elt))
69 (gensym (make-symbol "time")))
70 `(let* ,(append `((,gensym ,time-value)
76 (setq ,low (pop ,gensym))
78 ,(append `(setq ,micro (car ,gensym))
79 (when type `(,type 2)))
80 ,(append `(setq ,micro 0)
81 (when type `(,type 1)))))
82 ,(append `(setq ,low ,gensym ,micro 0)
83 (when type `(,type 0))))
84 (with-decoded-time-value ,varlist ,@body)))
87 (defun encode-time-value (high low micro type)
88 "Encode HIGH, LOW, and MICRO into a time value of type TYPE.
89 Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH LOW),
90 and type 3 is the list (HIGH LOW MICRO)."
92 ((eq type 0) (cons high low))
93 ((eq type 1) (list high low))
94 ((eq type 2) (list high low micro))))
96 (autoload 'parse-time-string "parse-time")
97 (autoload 'timezone-make-date-arpa-standard "timezone")
100 (defun date-to-time (date)
101 "Parse a string that represents a date-time and return a time value."
105 ;; `parse-time-string' isn't sufficiently general or
106 ;; robust. It fails to grok some of the formats that
107 ;; timezone does (e.g. dodgy post-2000 stuff from some
108 ;; Elms) and either fails or returns bogus values. Lars
109 ;; reverted this change, but that loses non-trivially
110 ;; often for me. -- fx
111 (timezone-make-date-arpa-standard date)))
112 (error (error "Invalid date: %s" date))))
114 (defun time-to-seconds (time)
115 "Convert time value TIME to a floating point number.
116 You can use `float-time' instead."
117 (with-decoded-time-value ((high low micro time))
118 (+ (* 1.0 high 65536)
120 (/ micro 1000000.0))))
123 (defun seconds-to-time (seconds)
124 "Convert SECONDS (a floating point number) to a time value."
125 (list (floor seconds 65536)
126 (floor (mod seconds 65536))
127 (floor (* (- seconds (ffloor seconds)) 1000000))))
130 (defun time-less-p (t1 t2)
131 "Say whether time value T1 is less than time value T2."
132 (with-decoded-time-value ((high1 low1 micro1 t1)
133 (high2 low2 micro2 t2))
138 (< micro1 micro2)))))))
141 (defun days-to-time (days)
142 "Convert DAYS into a time value."
143 (let* ((seconds (* 1.0 days 60 60 24))
144 (high (condition-case nil (floor (/ seconds 65536))
145 (range-error most-positive-fixnum))))
146 (list high (condition-case nil (floor (- seconds (* 1.0 high 65536)))
147 (range-error 65535)))))
150 (defun time-since (time)
151 "Return the time elapsed since TIME.
152 TIME should be either a time value or a date-time string."
154 ;; Convert date strings to internal time.
155 (setq time (date-to-time time)))
156 (time-subtract (current-time) time))
159 (defalias 'subtract-time 'time-subtract)
162 (defun time-subtract (t1 t2)
163 "Subtract two time values.
164 Return the difference in the format of a time value."
165 (with-decoded-time-value ((high low micro type t1)
166 (high2 low2 micro2 type2 t2))
167 (setq high (- high high2)
169 micro (- micro micro2)
170 type (max type type2))
173 micro (+ micro 1000000)))
177 (encode-time-value high low micro type)))
180 (defun time-add (t1 t2)
181 "Add two time values. One should represent a time difference."
182 (with-decoded-time-value ((high low micro type t1)
183 (high2 low2 micro2 type2 t2))
184 (setq high (+ high high2)
186 micro (+ micro micro2)
187 type (max type type2))
188 (when (>= micro 1000000)
190 micro (- micro 1000000)))
194 (encode-time-value high low micro type)))
197 (defun date-to-day (date)
198 "Return the number of days between year 1 and DATE.
199 DATE should be a date-time string."
200 (time-to-days (date-to-time date)))
203 (defun days-between (date1 date2)
204 "Return the number of days between DATE1 and DATE2.
205 DATE1 and DATE2 should be date-time strings."
206 (- (date-to-day date1) (date-to-day date2)))
209 (defun date-leap-year-p (year)
210 "Return t if YEAR is a leap year."
211 (or (and (zerop (% year 4))
212 (not (zerop (% year 100))))
213 (zerop (% year 400))))
216 (defun time-to-day-in-year (time)
217 "Return the day number within the year of the date month/day/year."
218 (let* ((tim (decode-time time))
222 (day-of-year (+ day (* 31 (1- month)))))
224 (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
225 (when (date-leap-year-p year)
226 (setq day-of-year (1+ day-of-year))))
230 (defun time-to-days (time)
231 "The number of days between the Gregorian date 0001-12-31bce and TIME.
232 TIME should be a time value.
233 The Gregorian date Sunday, December 31, 1bce is imaginary."
234 (let* ((tim (decode-time time))
238 (+ (time-to-day-in-year time) ; Days this year
239 (* 365 (1- year)) ; + Days in prior years
240 (/ (1- year) 4) ; + Julian leap years
241 (- (/ (1- year) 100)) ; - century years
242 (/ (1- year) 400)))) ; + Gregorian leap years
244 (defun time-to-number-of-days (time)
245 "Return the number of days represented by TIME.
246 The number of days will be returned as a floating point number."
247 (/ (time-to-seconds time) (* 60 60 24)))
250 (defun safe-date-to-time (date)
251 "Parse a string that represents a date-time and return a time value.
252 If DATE is malformed, return a time value of zeros."
259 ;;; time-date.el ends here