diff --git a/pkg/apis/core/annotation_key_constants.go b/pkg/apis/core/annotation_key_constants.go
index bbe0b92220d..bef73c0db0b 100644
--- a/pkg/apis/core/annotation_key_constants.go
+++ b/pkg/apis/core/annotation_key_constants.go
@@ -84,11 +84,11 @@ const (
 	AnnotationLoadBalancerSourceRangesKey = "service.beta.kubernetes.io/load-balancer-source-ranges"
 
 	// EndpointsLastChangeTriggerTime is the annotation key, set for endpoints objects, that
-	// represents the timestamp (expressed as a Unix time in milliseconds, i.e. the number of
-	// milliseconds elapsed since January 1, 1970 UTC) of the last change, of some pod or service
-	// object, that triggered the endpoints object change. In other words, if a Pod / Service changed
-	// at time T0, that change was observed by endpoints controller at T1, and the Endpoints object
-	// was changed at T2, the EndpointsLastChangeTriggerTime would be set to T0.
+	// represents the timestamp (stored as RFC 3339 date-time string, e.g. '2018-10-22T19:32:52.1Z')
+	// of the last change, of some Pod or Service object, that triggered the endpoints object change.
+	// In other words, if a Pod / Service changed at time T0, that change was observed by endpoints
+	// controller at T1, and the Endpoints object was changed at T2, the
+	// EndpointsLastChangeTriggerTime would be set to T0.
 	//
 	// The "endpoints change trigger" here means any Pod or Service change that resulted in the
 	// Endpoints object change.
diff --git a/staging/src/k8s.io/api/core/v1/annotation_key_constants.go b/staging/src/k8s.io/api/core/v1/annotation_key_constants.go
index 7a1088ad569..2c72ec2df2d 100644
--- a/staging/src/k8s.io/api/core/v1/annotation_key_constants.go
+++ b/staging/src/k8s.io/api/core/v1/annotation_key_constants.go
@@ -80,11 +80,11 @@ const (
 	AnnotationLoadBalancerSourceRangesKey = "service.beta.kubernetes.io/load-balancer-source-ranges"
 
 	// EndpointsLastChangeTriggerTime is the annotation key, set for endpoints objects, that
-	// represents the timestamp (expressed as a Unix time in milliseconds, i.e. the number of
-	// milliseconds elapsed since January 1, 1970 UTC) of the last change, of some pod or service
-	// object, that triggered the endpoints object change. In other words, if a Pod / Service changed
-	// at time T0, that change was observed by endpoints controller at T1, and the Endpoints object
-	// was changed at T2, the EndpointsLastChangeTriggerTime would be set to T0.
+	// represents the timestamp (stored as RFC 3339 date-time string, e.g. '2018-10-22T19:32:52.1Z')
+	// of the last change, of some Pod or Service object, that triggered the endpoints object change.
+	// In other words, if a Pod / Service changed at time T0, that change was observed by endpoints
+	// controller at T1, and the Endpoints object was changed at T2, the
+	// EndpointsLastChangeTriggerTime would be set to T0.
 	//
 	// The "endpoints change trigger" here means any Pod or Service change that resulted in the
 	// Endpoints object change.