--- ext/date/date_core.c.orig	2012-03-30 14:15:10.000000000 +0900
+++ ext/date/date_core.c	2013-02-18 01:33:31.000000000 +0900
@@ -7864,7 +7864,7 @@
     of = tm.tm_gmtoff;
 #elif defined(HAVE_VAR_TIMEZONE)
 #ifdef HAVE_VAR_ALTZONE
-    of = (long)((tm.tm_isdst > 0) ? altzone : timezone);
+    of = (long)-((tm.tm_isdst > 0) ? altzone : timezone);
 #else
     of = (long)-timezone;
     if (tm.tm_isdst) {