[tracker] libtracker-common: Fix localtime handling with historic UTC offsets

[Jürg Billeter <juergbi src gnome org>]

commit 0e5ae8fa2636d3e33ef59258a7ff5fd7cdb820ba
Author: Jürg Billeter <j bitron ch>
Date:   Thu Mar 24 15:55:07 2011 +0100

    libtracker-common: Fix localtime handling with historic UTC offsets

 src/libtracker-common/tracker-date-time.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/src/libtracker-common/tracker-date-time.c b/src/libtracker-common/tracker-date-time.c
index 46e05f2..49412c0 100644
--- a/src/libtracker-common/tracker-date-time.c
+++ b/src/libtracker-common/tracker-date-time.c
@@ -158,12 +158,21 @@ tracker_string_to_date (const gchar *date_string,
 			t -= offset;
 		}
 	} else {
+		time_t t2;
+
 		/* local time */
 		tm.tm_isdst = -1;
 
 		t = mktime (&tm);
 
+		/* calculate UTC offset, requires timegm for correct result
+		   with past times when timezone had different UTC offset */
+#if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined (__GLIBC__))
 		offset = -timezone + (tm.tm_isdst > 0 ? 3600 : 0);
+#else
+		t2 = timegm (&tm);
+		offset = t2 - t;
+#endif
 	}
 
 	g_match_info_free (match_info);