tm.tm_zone is non-standard.

src/unittest_timestamp.cc

@@ -9,11 +9,10 @@ namespace std
 	ostream& operator<<(ostream& o, struct tm const& t)
 	{
 		char buf[80];
-		snprintf(buf, 79, "<%04d-%02d-%02d %02d:%02d:%02d wday=%d yday=%d isdst=%d zone=%s>",
+		snprintf(buf, 79, "<%04d-%02d-%02d %02d:%02d:%02d wday=%d yday=%d isdst=%d>",
 			t.tm_year+1900, t.tm_mon+1, t.tm_mday,
 			t.tm_hour, t.tm_min, t.tm_sec,
 			t.tm_wday, t.tm_yday, t.tm_isdst,
-			(t.tm_zone ? t.tm_zone : "(NULL)")
 			);
 		return o << buf;
 	}