diff --git a/pkg/apis/core/annotation_key_constants.go b/pkg/apis/core/annotation_key_constants.go
index fb2751803e0..bbac9189b1d 100644
--- a/pkg/apis/core/annotation_key_constants.go
+++ b/pkg/apis/core/annotation_key_constants.go
@@ -84,7 +84,7 @@ const (
 	AnnotationLoadBalancerSourceRangesKey = "service.beta.kubernetes.io/load-balancer-source-ranges"
 
 	// EndpointsLastTriggerTime is the annotation key, set for endpoints objects, that represents the
-	// timestamp of the last change that triggered the endpoints object update.
+	// timestamp (in milliseconds) of the last change that triggered the endpoints object update.
 	// This annotation will be used to compute the in-cluster network programming SLI. See
 	// https://github.com/kubernetes/community/blob/master/sig-scalability/slos/network_programming_latency.md
 	EndpointsLastTriggerTime = "kubernetes.io/endpoints.last-trigger-time"
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 f4830cbe199..c8add833da3 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
@@ -80,7 +80,7 @@ const (
 	AnnotationLoadBalancerSourceRangesKey = "service.beta.kubernetes.io/load-balancer-source-ranges"
 
 	// EndpointsLastTriggerTime is the annotation key, set for endpoints objects, that represents the
-	// timestamp of the last change that triggered the endpoints object update.
+	// timestamp (in milliseconds) of the last change that triggered the endpoints object update.
 	// This annotation will be used to compute the in-cluster network programming SLI. See
 	// https://github.com/kubernetes/community/blob/master/sig-scalability/slos/network_programming_latency.md
 	EndpointsLastTriggerTime = "kubernetes.io/endpoints.last-trigger-time"