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From: minow@mountn.dec.com (Martin Minow)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Time ain't on my side
Keywords: time, time zone, map
Message-ID: <1815@mountn.dec.com>
Date: 3 Aug 90 00:29:49 GMT
References: <1990Aug2.003955.4443@ux1.cso.uiuc.edu>
Reply-To: minow@bolt.enet.dec.com (Martin Minow)
Distribution: comp
Organization: Digital Equipment Corporation
Lines: 29

In article <1990Aug2.003955.4443@ux1.cso.uiuc.edu>
resnick@lees.cogsci.uiuc.edu (Pete Resnick) writes:
>
>Is there any way to access the time zone from the "Map" cdev. It
>says in the documentation (when was the last time any of you looked
>in the Macintosh Utilties User's Guide, p, 124):

I wrote an article on this for MacTutor (September-ish 1989 -- it's in
a recent "Best of" collection.  You might also find the info in the
latest ScriptManager documentation (check the Sumex archives or apple.com
archives or bug a certified developer).  Essentially, the info the Map
CDEV uses is stored in the parameter RAM.  Time zone is stored as "seconds
offset from UTC (GMT)" in 24 bits.  I think the high byte is reserved for
a daylight savings time flag of some sort.

>
>Also, is there anything in System Software for determining daylight
>savings rules? If not, does anyone know the official rules, or know
>how to get them from the time gods in France, or wherever they may be?
>
Not that I know of.  There may be a collection of Daylight Savings Time rules
floating around the Unix source library part of Usenet: one of the
archive sites might have more info.  The rules are messy and very subject
to change.  In fact, in some instances (Arizona, for example), they are
so messy as to be useless.  (In Arizona, "government owned" land follows
daylight savings time rules, while non-government land does not.)

Martin Minow
minow@bolt.enet.dec.com