diff --git a/ext/date/date_core.c b/ext/date/date_core.c
index 4a2225fd2c..146f60fef6 100644
--- a/ext/date/date_core.c
+++ b/ext/date/date_core.c
@@ -7797,7 +7797,7 @@ datetime_s_now(int argc, VALUE *argv, VALUE klass)
 #ifdef HAVE_STRUCT_TM_TM_GMTOFF
     of = tm.tm_gmtoff;
 #elif defined(HAVE_TIMEZONE)
-#ifdef HAVE_ALTZONE
+#if defined(HAVE_ALTZONE) && !defined(_AIX)
     of = (long)-((tm.tm_isdst > 0) ? altzone : timezone);
 #else
     of = (long)-timezone;