diff --git a/zic.c b/zic.c
index 5968fa5..a049818 100644
--- a/zic.c
+++ b/zic.c
@@ -931,6 +931,8 @@ const int		signable;
 			error(errstring);
 			return 0;
 	}
+	if (noise && hh == HOURSPERDAY)
+		warning(_("24:00 not handled by pre-1998 versions of zic"));
 	return eitol(sign) *
 		(eitol(hh * MINSPERHOUR + mm) *
 		eitol(SECSPERMIN) + eitol(ss));