diff --git a/python/ray/autoscaler/v2/tests/test_sdk.py b/python/ray/autoscaler/v2/tests/test_sdk.py
index 81e9422583e8..ca26453d9610 100644
--- a/python/ray/autoscaler/v2/tests/test_sdk.py
+++ b/python/ray/autoscaler/v2/tests/test_sdk.py
@@ -1,5 +1,6 @@
 import os
 import sys
+import time
 
 # coding: utf-8
 from dataclasses import dataclass
@@ -102,7 +103,7 @@ def verify():
 
 
 def test_node_state_lifecycle_basic(ray_start_cluster):
-
+    start_s = time.perf_counter()
     cluster = ray_start_cluster
     cluster.add_node(num_cpus=0)
     ray.init(address=cluster.address)
@@ -174,13 +175,22 @@ def verify_cluster_busy():
     # Kill the node.
     cluster.remove_node(node)
 
+    # Sleep for a bit so head node should be idle longer than this.
+    time.sleep(3)
+
     def verify_cluster_no_node():
         state = get_cluster_resource_state(stub)
+        now_s = time.perf_counter()
+        test_dur_ms = (now_s - start_s) * 1000
         assert_node_states(
             state,
             [
                 NodeState(node_id, NodeStatus.DEAD),
-                NodeState(head_node_id, NodeStatus.IDLE, lambda idle_ms: idle_ms > 0),
+                NodeState(
+                    head_node_id,
+                    NodeStatus.IDLE,
+                    lambda idle_ms: idle_ms > 3 * 1000 and idle_ms < test_dur_ms,
+                ),
             ],
         )
         return True
diff --git a/src/ray/gcs/gcs_server/gcs_autoscaler_state_manager.cc b/src/ray/gcs/gcs_server/gcs_autoscaler_state_manager.cc
index 21b7c73fadf7..0d93792212a9 100644
--- a/src/ray/gcs/gcs_server/gcs_autoscaler_state_manager.cc
+++ b/src/ray/gcs/gcs_server/gcs_autoscaler_state_manager.cc
@@ -200,10 +200,21 @@ void GcsAutoscalerStateManager::GetNodeStates(
     auto const &node_resource_data = cluster_resource_manager_.GetNodeResources(
         scheduling::NodeID(node_state_proto->node_id()));
     if (node_resource_data.idle_resource_duration_ms > 0) {
-      // The node is idle.
+      // The node was reported idle.
       node_state_proto->set_status(rpc::autoscaler::NodeStatus::IDLE);
+
+      // We approximate the idle duration by the time since the last idle report
+      // plus the idle duration reported by the node:
+      //  idle_dur = <idle-dur-reported-by-raylet> + <time-since-gcs-gets-last-report>
+      //
+      // This is because with lightweight resource update, we don't keep reporting
+      // the idle time duration when there's no resource change. We also don't want to
+      // use raylet reported idle timestamp since there might be clock skew.
+      RAY_CHECK(node_resource_data.last_resource_update_time != absl::nullopt);
       node_state_proto->set_idle_duration_ms(
-          node_resource_data.idle_resource_duration_ms);
+          node_resource_data.idle_resource_duration_ms +
+          absl::ToInt64Milliseconds(
+              absl::Now() - node_resource_data.last_resource_update_time.value()));
     } else {
       node_state_proto->set_status(rpc::autoscaler::NodeStatus::RUNNING);
     }
diff --git a/src/ray/raylet/scheduling/cluster_resource_data.h b/src/ray/raylet/scheduling/cluster_resource_data.h
index fb8c9e5fdc31..fbb5e0aba8c2 100644
--- a/src/ray/raylet/scheduling/cluster_resource_data.h
+++ b/src/ray/raylet/scheduling/cluster_resource_data.h
@@ -436,9 +436,12 @@ class NodeResources {
   // The key-value labels of this node.
   absl::flat_hash_map<std::string, std::string> labels;
 
-  // The idle duration of the node from resources.
+  // The idle duration of the node from resources reported by raylet.
   int64_t idle_resource_duration_ms = 0;
 
+  // The timestamp of the last resource update if there was a resource report.
+  absl::optional<absl::Time> last_resource_update_time = absl::nullopt;
+
   /// Normal task resources could be uploaded by 1) Raylets' periodical reporters; 2)
   /// Rejected RequestWorkerLeaseReply. So we need the timestamps to decide whether an
   /// upload is latest.
diff --git a/src/ray/raylet/scheduling/cluster_resource_manager.cc b/src/ray/raylet/scheduling/cluster_resource_manager.cc
index 78bdfa18c2d6..295dde4c2c9b 100644
--- a/src/ray/raylet/scheduling/cluster_resource_manager.cc
+++ b/src/ray/raylet/scheduling/cluster_resource_manager.cc
@@ -256,6 +256,9 @@ bool ClusterResourceManager::UpdateNodeAvailableResourcesIfExist(
 
   // Update the idle duration for the node in terms of resources usage.
   node_resources->idle_resource_duration_ms = resource_data.idle_duration_ms();
+
+  // Last update time to the local node resources view.
+  node_resources->last_resource_update_time = absl::Now();
   return true;
 }