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From: Makey@logicon.arpa (Jeff Makey)
Newsgroups: net.lang.c
Subject: Re: ANSI C.
Message-ID: <3508@brl-tgr.ARPA>
Date: Fri, 22-Nov-85 19:51:46 EST
Article-I.D.: brl-tgr.3508
Posted: Fri Nov 22 19:51:46 1985
Date-Received: Sun, 24-Nov-85 07:06:01 EST
Sender: news@brl-tgr.ARPA
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The daylight time flag returned by localtime() does NOT have to be
provided by the operating system.  I looked at the 10-year-old source
code on my PDP-11/70 PWB UNIX system (no environment variables) and
observed that localtime() *computes* whether or not the date it is
processing is between the last Sundays in April and October.  The ONLY
input to localtime() (it makes no system calls) is a GMT date/time
value that is immediately converted to local standard time, then to
daylight time if appropriate.  There are static variables that are
hard-coded to indicate: the difference in hours between GMT and local
standard time; and whether or not conversion to daylight time should
ever occur (useful throughout most of Indiana, where they are always on
eastern standard time).

                            :: Jeff Makey
                               Makey@LOGICON.ARPA