;;; -*- Mode:Lisp; Readtable:ZL; Package:USER; Base:10; Patch-File:T -*-
;;; Patch file for System version 121.60
;;; Reason:
;;;  Daylight savings time was in effect ONLY during certain weeks of April and October.
;;; Written 1-May-87 09:59:00 by pld (Peter L. DeWolf) at site LMI Cambridge
;;; while running on Azathoth from band 3
;;; with Experimental System 121.58, Experimental Lambda-Diag 15.0, Experimental ZMail 70.2, Experimental KERMIT 32.0, Experimental Unix-Interface 10.0, Experimental Local-File 72.0, Experimental FILE-Server 21.0, Experimental Tape 13.0, microcode 1742, SDU Boot Tape 3.12, SDU ROM 102, the old ones.



; From modified file DJ: L.IO1; TIME.LISP#138 at 1-May-87 09:59:01
#10R TIME#: 
(COMPILER-LET ((*PACKAGE* (PKG-FIND-PACKAGE "TIME")))
  (COMPILER::PATCH-SOURCE-FILE "SYS: IO1; TIME  "

(defun daylight-savings-time-in-usa-p (seconds minutes hours day month year)
  (declare (ignore seconds minutes))
  ;;; remember, HOURS here is always in standard time.
  (cond ((< month 4) nil)			; before April
	((> month 10.) nil)			; after October
	((= month 4)
	 (let ((magic-day (cond ((< year 1987.) (last-sunday-in-april year))
				((>= year 1987.) (first-sunday-in-april year)))))
	   (cond ((< day magic-day) nil)
		 ((> day magic-day) t)
		 ((>= hours 2) t)
		 (t nil))))
	((= month 10.)
	 (let ((magic-day (last-sunday-in-october year)))
	   (cond ((< day magic-day) t)
		 ((> day magic-day) nil)
		 ((>= hours 1) nil)
		 (t t))))
	(t t)))

))