1 ;;; time-date.el --- Date and time handling functions
2 ;; Copyright (C) 1998,99 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.
31 (autoload 'timezone-make-date-arpa-standard "timezone")
34 (defun date-to-time (date)
35 "Convert DATE into time."
37 ;; `timezone-make-date-arpa-standard' makes this more robust,
38 ;; e.g. against the crop of year 100 dates in Jan 2000.
39 (apply 'encode-time (parse-time-string
40 (timezone-make-date-arpa-standard date)))
41 (error (error "Invalid date: %s" date))))
43 (defun time-to-seconds (time)
44 "Convert TIME to a floating point number."
45 (+ (* (car time) 65536.0)
47 (/ (or (nth 2 time) 0) 1000000.0)))
49 (defun seconds-to-time (seconds)
50 "Convert SECONDS (a floating point number) to an Emacs time structure."
51 (list (floor seconds 65536)
52 (floor (mod seconds 65536))
53 (floor (* (- seconds (ffloor seconds)) 1000000))))
55 (defun time-less-p (t1 t2)
56 "Say whether time T1 is less than time T2."
57 (or (< (car t1) (car t2))
58 (and (= (car t1) (car t2))
59 (< (nth 1 t1) (nth 1 t2)))))
61 (defun days-to-time (days)
62 "Convert DAYS into time."
63 (let* ((seconds (* 1.0 days 60 60 24))
65 (ms (condition-case nil (floor (/ seconds rest))
66 (range-error (expt 2 16)))))
67 (list ms (condition-case nil (round (- seconds (* ms rest)))
68 (range-error (expt 2 16))))))
70 (defun time-since (time)
71 "Return the time since TIME, which is either an internal time or a date."
73 ;; Convert date strings to internal time.
74 (setq time (date-to-time time)))
75 (let* ((current (current-time))
76 (rest (when (< (nth 1 current) (nth 1 time))
78 (list (- (+ (car current) (if rest -1 0)) (car time))
79 (- (+ (or rest 0) (nth 1 current)) (nth 1 time)))))
81 (defun subtract-time (t1 t2)
82 "Subtract two internal times."
83 (let ((borrow (< (cadr t1) (cadr t2))))
84 (list (- (car t1) (car t2) (if borrow 1 0))
85 (- (+ (if borrow 65536 0) (cadr t1)) (cadr t2)))))
87 (defun date-to-day (date)
88 "Return the number of days between year 1 and DATE."
89 (time-to-days (date-to-time date)))
91 (defun days-between (date1 date2)
92 "Return the number of days between DATE1 and DATE2."
93 (- (date-to-day date1) (date-to-day date2)))
95 (defun date-leap-year-p (year)
96 "Return t if YEAR is a leap year."
97 (or (and (zerop (% year 4))
98 (not (zerop (% year 100))))
99 (zerop (% year 400))))
101 (defun time-to-day-in-year (time)
102 "Return the day number within the year of the date month/day/year."
103 (let* ((tim (decode-time time))
107 (day-of-year (+ day (* 31 (1- month)))))
109 (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
110 (when (date-leap-year-p year)
111 (setq day-of-year (1+ day-of-year))))
114 (defun time-to-days (time)
115 "The number of days between the Gregorian date 0001-12-31bce and TIME.
116 The Gregorian date Sunday, December 31, 1bce is imaginary."
117 (let* ((tim (decode-time time))
121 (+ (time-to-day-in-year time) ; Days this year
122 (* 365 (1- year)) ; + Days in prior years
123 (/ (1- year) 4) ; + Julian leap years
124 (- (/ (1- year) 100)) ; - century years
125 (/ (1- year) 400)))) ; + Gregorian leap years
128 (defun safe-date-to-time (date)
129 "Parse DATE and return a time structure.
130 If DATE is malformed, a zero time will be returned."
137 ;;; time-date.el ends here