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Commit 22765cd4 authored by Kevin M. Rosenberg's avatar Kevin M. Rosenberg
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r11722: add day-of-week

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01 Jun 2007 Kevin Rosenberg <kevin@rosenberg.net>
* datetime.lisp: Add day-of-week
07 Jan 2007 Kevin Rosenberg <kevin@rosenberg.net> 07 Jan 2007 Kevin Rosenberg <kevin@rosenberg.net>
* Version 1.94 * Version 1.94
* signals.lisp: Conditionalize Lispworks support to :unix *features* * signals.lisp: Conditionalize Lispworks support to :unix *features*
......
...@@ -32,7 +32,7 @@ ...@@ -32,7 +32,7 @@
"July" "August" "September" "October" "November" "July" "August" "September" "October" "November"
"December") "December")
(1- mn)) (1- mn))
(format nil "~A" dy) (format nil "~A" dy)
(format nil "~A" yr) (format nil "~A" yr)
(format nil "~2,'0D:~2,'0D:~2,'0D" hr min sec)))) (format nil "~2,'0D:~2,'0D:~2,'0D" hr min sec))))
...@@ -108,6 +108,20 @@ ...@@ -108,6 +108,20 @@
mincol colinc minpad padchar mincol colinc minpad padchar
(subseq monthstring 0 truncate))))) (subseq monthstring 0 truncate)))))
(defconstant* +zellers-adj+ #(0 3 2 5 0 3 5 1 4 6 2 4))
(defun day-of-week (year month day)
"Day of week calculation using Zeller's Congruence.
Input: The year y, month m (1 ≤ m ≤ 12) and day d (1 ≤ d ≤ 31).
Output: n - the day of the week (Sunday = 0, Saturday = 6)."
(when (< month 3)
(decf year))
(mod
(+ year (floor year 4) (- (floor year 100)) (floor year 400)
(aref +zellers-adj+ (1- month)) day)
7))
;;;; Daylight Saving Time calculations ;;;; Daylight Saving Time calculations
;; Daylight Saving Time begins for most of the United States at 2 ;; Daylight Saving Time begins for most of the United States at 2
......
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