Function: math-std-daylight-savings-new

math-std-daylight-savings-new is a byte-compiled function defined in calc-forms.el.gz.

Signature

(math-std-daylight-savings-new DATE DT ZONE BUMP)

Documentation

Standard North American daylight saving algorithm as of 2007.

This implements the rules for the U.S. and Canada. Daylight saving begins on the second Sunday of March at 2 a.m., and ends on the first Sunday of November at 2 a.m.

Source Code

;; Defined in /usr/src/emacs/lisp/calc/calc-forms.el.gz
(defun math-std-daylight-savings-new (date dt _zone bump)
  "Standard North American daylight saving algorithm as of 2007.
This implements the rules for the U.S. and Canada.
Daylight saving begins on the second Sunday of March at 2 a.m.,
and ends on the first Sunday of November at 2 a.m."
  (cond ((< (nth 1 dt) 3) 0)
	((= (nth 1 dt) 3)
	 (let ((sunday (math-prev-weekday-in-month date dt 14 0)))
	   (cond ((< (nth 2 dt) sunday) 0)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 3 bump)) -1 0))
		 (t -1))))
	((< (nth 1 dt) 11) -1)
	((= (nth 1 dt) 11)
	 (let ((sunday (math-prev-weekday-in-month date dt 7 0)))
	   (cond ((< (nth 2 dt) sunday) -1)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 2 bump)) 0 -1))
		 (t 0))))
	(t 0)))