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From: "Luca Wullschleger" <luca DOT wullschleger AT epfl DOT ch>
To: <cygwin AT cygwin DOT com>
Subject: strptime error when setting a different TimeZone with export TZ=UTC
Date: Fri, 24 Jun 2005 20:18:03 +0200
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Hi everybody. I have a very specific problem and I'm looking for someone
giving me a solution.
 
When I set the TZ environment varialbe TZ to "UTC" and try to execute "date"
I get the right date in UTC format:

**************** begin
$ date
Fri Jun 24 20:13:05 WEDT 2005
$ export TZ=UTC
$ date
Fri Jun 24 18:03:00 UTC 2005
**************** end
 
But if I try to execute the peace of code written in C here below, I have a
very strange behaviour.

**************** begin
$ ./test_time
Timezone:       WEST-1WEDT-2,M3.5.0/2,M10.5.0/3

TS =            1097712000
LOCAL :         Thu Oct 14 02:00:00 2004
UTC :           Thu Oct 14 00:00:00 2004

Trying with '13/Oct/2004:17:00:00 -0700' -> 1097712000
ts =            1097704800
LOCAL :         Thu Oct 14 00:00:00 2004
UTC :           Wed Oct 13 22:00:00 2004

$ export TZ=UTC
$ ./test_time
Timezone:       UTC

TS =            1097712000
LOCAL :         Thu Oct 14 00:00:00 2004
UTC :           Thu Oct 14 00:00:00 2004

Trying with '13/Oct/2004:17:00:00 -0700' -> 1097712000
ts =            25199
LOCAL :         Thu Jan  1 06:59:59 1970                       <-- problem
UTC :           Thu Jan  1 06:59:59 1970                       <-- problem
**************** end

As you can see the problem is in in the last 2 lines..
I would like to be able to parse the date in UTC, but it seams that either
the strptime or the mktime function do not like the modification of the TZ
environment variable.

I also tried to printout the broken-down date structure try and it seams to
be correct, so I suppose that the problem is with the mktime() function. I
know this mktime() function uses some timezone settings from somewhere.

I executed this peace of code on a Linux machine and the behaviour is right.
It seams that the problem only occurs within Cygwin.

I tried everything, google searched it, but I found nothing interesting.

Any idea?

Thanks a lot for the help... 

Luca

Email: luca DOT wullschleger AT epfl DOT ch



**************** file test_time.c

#include <stdlib.h>
#include <stdio.h>
#include <zlib.h>
#include <time.h>

/** Main method.
 */
int main(int argc, char **argv) {
	
	tzset();
	printf("Timezone:       %s\n\n",getenv("TZ"));
	
	time_t ts = 1097712000;  /* "13/Oct/2004:17:30:00" */
	printf("TS =            %i\n",(int)ts);
	printf("LOCAL :         %s", asctime(localtime(&ts)));
	printf("UTC :           %s", asctime(gmtime(&ts)));
	
	printf("\nTrying with '13/Oct/2004:17:00:00 -0700' ->
1097712000\n");
	struct tm try;
	time_t ts2;
	char date[30] = "13/Oct/2004:17:30:00";
	char timezone[4] = "-07";

	if ((char *)strptime(date,"%d/%b/%Y:%T",&try) == NULL) {
		printf("Error with strptime\n");
		return 1;
	}
	ts2 = mktime(&try) - atoi(timezone)*3600;
	printf("ts =            %i\n",(int)ts2);
	printf("LOCAL :         %s", asctime(localtime(&ts2)));	
	printf("UTC :           %s", asctime(gmtime(&ts2)));
	
	return (0);
}




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