diff --git a/harness/temporalHelpers.js b/harness/temporalHelpers.js
index b4c0fb1604..be21846e74 100644
--- a/harness/temporalHelpers.js
+++ b/harness/temporalHelpers.js
@@ -1105,6 +1105,10 @@ var TemporalHelpers = {
         "11-18[U-CA=iso8601]",
         "11-18[u-CA=iso8601]",
         "11-18[FOO=bar]",
+        "-999999-01-01[u-ca=gregory]",
+        "-999999-01-01[u-ca=chinese]",
+        "+999999-01-01[u-ca=gregory]",
+        "+999999-01-01[u-ca=chinese]",
       ];
     },
 
@@ -1136,6 +1140,10 @@ var TemporalHelpers = {
         "1976-10-01",
         "--10-01",
         "--1001",
+        "-999999-10-01",
+        "-999999-10-01[u-ca=iso8601]",
+        "+999999-10-01",
+        "+999999-10-01[u-ca=iso8601]",
       ];
     },