Date: Thu, 17 Oct 2002 21:21:34 -0700 (PDT) From: =?ISO-8859-1?Q?Mikko_Ty=F6l=E4j=E4rvi?= <mbsd@pacbell.net> To: Boris Kovalenko <boris@ntmk.ru> Cc: freebsd-stable@freebsd.org Subject: Re: mktime problem? Message-ID: <20021017211459.L308-100000@atlas.home> In-Reply-To: <3DAF7D3A.7060603@ntmk.ru>
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On Fri, 18 Oct 2002, Boris Kovalenko wrote:
> Hello!
>
> First the simple source code:
> #include <stdio.h>
> #include <sys/time.h>
>
> int main(int argc, char **argv)
> {
> time_t today = time( NULL );
> struct tm temp = *localtime( &today );
>
> temp.tm_hour = 24;
> temp.tm_min = 0;
> temp.tm_sec = 0;
> temp.tm_mday = 27;
printf("is dst = %d\n", temp.tm_isdst);
temp.tm_isdst = -1;
>
> today = mktime( &temp );
> printf("%s\n", ctime( &today ));
> return 0;
> }
>
> I expect 28 Oct 00:00, but got 27 Oct 23:00. Why? Daylight saving should
> be at 28 Oct 02:00? My zoneinfo is Yekaterinburg.
Seems to be intentional:
% man mktime
[...]
"A positive or zero value for tm_isdst causes mktime() to presume
initially that summer time (for example, Daylight Saving Time) is or
is not in effect for the specified time, respectively. A negative
value for tm_isdst causes the mktime() function to attempt to divine
whether summer time is in effect for the specified time."
Looks like a verbatim copy of the text in IEEE Std 1003.1-2001 (SUSv3).
$.02,
/Mikko
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