Hi Jeff: Am 27.03.17 15:28 schrieb(en) Jeffrey Stedfast via balsa-list:
When the timezone is "EDT" or "-0400", g_time_zone_new(const char *name) returns a GTimeZone just fine and I pass it off to g_date_time_new(), but if I then ask for the UTC offset from the GDateTime, I get back 0.If I change the string to "EST" or "-0500", everything works perfectly and I get back exactly the UTC offset that I would expect (-5 hours).
I guess the GLib functions (like tzset) use the iana zone info data base (<https://www.iana.org/time-zones>). On my Ubuntu 16.04 system it is living in the folder /usr/share/zoneinfo. But there is no "EDT" (or other daylight saving, like CEST) definition file. I wrote the tiny attached test app - passing "EDT" or "CEST" as 1st parameter fails as you described. Passing "EST" or "CET" or *any* numerical offset, including "-0400", returns the proper result. If the time zone names are given, of course depending upon the input date: ---8<---------------------------------------------------------------------------------- albrecht@deneb:~/Work$ ./gdatetimetest CET $(date +%s) ** Message: 1490643491 = 19:38:11 2017-03-27: interval 95: offset vs. UTC = 120 minutes albrecht@deneb:~/Work$ ./gdatetimetest CET 1490000000 ** Message: 1490000000 = 08:53:20 2017-03-20: interval 94: offset vs. UTC = 60 minutes albrecht@deneb:~/Work$ ./gdatetimetest +0100 $(date +%s) ** Message: 1490643494 = 19:38:14 2017-03-27: interval 0: offset vs. UTC = 60 minutes ---8<---------------------------------------------------------------------------------- Do you get a different result when using the pure libc functions (i.e. set TZ, use tzset(), and then localtime())? At least running the "date" command from the console with TZ set to a dst time zone will /also/ return UTC: ---8<---------------------------------------------------------------------------------- albrecht@deneb:~/Work$ TZ=CET date Mo 27. Mär 21:53:22 CEST 2017 albrecht@deneb:~/Work$ TZ=CEST date Mo 27. Mär 19:53:24 CEST 2017 albrecht@deneb:~/Work$ TZ=UTC date Mo 27. Mär 19:53:37 UTC 2017 ---8<---------------------------------------------------------------------------------- Hope this helps, Albrecht.
#include <glib.h>
#include <time.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
GTimeZone *tz;
time_t ref_time;
char buf[64];
gint interval;
g_assert(argc >= 3);
tz = g_time_zone_new(argv[1]);
ref_time = (time_t) strtol(argv[2], NULL, 0);
interval = g_time_zone_find_interval(tz, G_TIME_TYPE_UNIVERSAL, ref_time);
strftime(buf, sizeof(buf), "%T %F", gmtime(&ref_time));
g_message("%ld = %s: interval %d: offset vs. UTC = %d minutes",
(long int) ref_time, buf, interval, g_time_zone_get_offset(tz, interval) / 60);
g_time_zone_unref(tz);
return 0;
}
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