1 ;;; time-date.el --- Date and time handling functions
2 ;; Copyright (C) 1998, 1999, 2000 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.
32 (defun date-to-time (date)
33 "Convert DATE into time."
35 (apply 'encode-time
(parse-time-string date
))
36 (error (error "Invalid date: %s" date
))))
38 (defun time-to-seconds (time)
39 "Convert TIME to a floating point number."
40 (+ (* (car time
) 65536.0)
42 (/ (or (nth 2 time
) 0) 1000000.0)))
44 (defun seconds-to-time (seconds)
45 "Convert SECONDS (a floating point number) to an Emacs time structure."
46 (list (floor seconds
65536)
47 (floor (mod seconds
65536))
48 (floor (* (- seconds
(ffloor seconds
)) 1000000))))
50 (defun time-less-p (t1 t2
)
51 "Say whether time T1 is less than time T2."
52 (or (< (car t1
) (car t2
))
53 (and (= (car t1
) (car t2
))
54 (< (nth 1 t1
) (nth 1 t2
)))))
56 (defun days-to-time (days)
57 "Convert DAYS into time."
58 (let* ((seconds (* 1.0 days
60 60 24))
60 (ms (condition-case nil
(floor (/ seconds rest
))
61 (range-error (expt 2 16)))))
62 (list ms
(condition-case nil
(round (- seconds
(* ms rest
)))
63 (range-error (expt 2 16))))))
65 (defun time-since (time)
66 "Return the time since TIME, which is either an internal time or a date."
68 ;; Convert date strings to internal time.
69 (setq time
(date-to-time time
)))
70 (let* ((current (current-time))
71 (rest (when (< (nth 1 current
) (nth 1 time
))
73 (list (- (+ (car current
) (if rest -
1 0)) (car time
))
74 (- (+ (or rest
0) (nth 1 current
)) (nth 1 time
)))))
76 (defun subtract-time (t1 t2
)
77 "Subtract two internal times."
78 (let ((borrow (< (cadr t1
) (cadr t2
))))
79 (list (- (car t1
) (car t2
) (if borrow
1 0))
80 (- (+ (if borrow
65536 0) (cadr t1
)) (cadr t2
)))))
82 (defun date-to-day (date)
83 "Return the number of days between year 1 and DATE."
84 (time-to-days (date-to-time date
)))
86 (defun days-between (date1 date2
)
87 "Return the number of days between DATE1 and DATE2."
88 (- (date-to-day date1
) (date-to-day date2
)))
90 (defun date-leap-year-p (year)
91 "Return t if YEAR is a leap year."
92 (or (and (zerop (% year
4))
93 (not (zerop (% year
100))))
94 (zerop (% year
400))))
96 (defun time-to-day-in-year (time)
97 "Return the day number within the year of the date month/day/year."
98 (let* ((tim (decode-time time
))
102 (day-of-year (+ day
(* 31 (1- month
)))))
104 (setq day-of-year
(- day-of-year
(/ (+ 23 (* 4 month
)) 10)))
105 (when (date-leap-year-p year
)
106 (setq day-of-year
(1+ day-of-year
))))
109 (defun time-to-days (time)
110 "The number of days between the Gregorian date 0001-12-31bce and TIME.
111 The Gregorian date Sunday, December 31, 1bce is imaginary."
112 (let* ((tim (decode-time time
))
116 (+ (time-to-day-in-year time
) ; Days this year
117 (* 365 (1- year
)) ; + Days in prior years
118 (/ (1- year
) 4) ; + Julian leap years
119 (- (/ (1- year
) 100)) ; - century years
120 (/ (1- year
) 400)))) ; + Gregorian leap years
123 (defun safe-date-to-time (date)
124 "Parse DATE and return a time structure.
125 If DATE is malformed, a zero time will be returned."
132 ;;; time-date.el ends here