diff --git a/src/darwin/Framework/CHIP/MTRDevice.mm b/src/darwin/Framework/CHIP/MTRDevice.mm
index 9ca065238b4dd3..ca1bfd6495b03d 100644
--- a/src/darwin/Framework/CHIP/MTRDevice.mm
+++ b/src/darwin/Framework/CHIP/MTRDevice.mm
@@ -156,6 +156,8 @@ @interface MTRDevice ()
 
 @property (nonatomic) BOOL expirationCheckScheduled;
 
+@property (nonatomic) NSDate * estimatedStartTimeFromGeneralDiagnosticsUpTime;
+
 /**
  * If currentReadClient is non-null, that means that we successfully
  * called SendAutoResubscribeRequest on the ReadClient and have not yet gotten
@@ -260,7 +262,9 @@ - (void)_changeState:(MTRDeviceState)state
     _state = state;
     if (lastState != state) {
         if (state != MTRDeviceStateReachable) {
+            MTR_LOG_INFO("%@ Set estimated start time to nil due to state change", self);
             _estimatedStartTime = nil;
+            _estimatedStartTimeFromGeneralDiagnosticsUpTime = nil;
         }
         id<MTRDeviceDelegate> delegate = _weakDelegate.strongObject;
         if (delegate) {
@@ -412,8 +416,18 @@ - (void)_handleEventReport:(NSArray<NSDictionary<NSString *, id> *> *)eventRepor
         MTREventPath * eventPath = eventDict[MTREventPathKey];
         BOOL isStartUpEvent = (eventPath.cluster.unsignedLongValue == MTRClusterIDTypeBasicInformationID)
             && (eventPath.event.unsignedLongValue == MTREventIDTypeClusterBasicInformationEventStartUpID);
-        if (isStartUpEvent) {
-            _estimatedStartTime = nil;
+        if (isStartUpEvent && (_state == MTRDeviceStateReachable)) {
+            // StartUp event received when server resumes subscription
+            if (_estimatedStartTimeFromGeneralDiagnosticsUpTime) {
+                // If UpTime was received, make use of it as mark of system start time
+                MTR_LOG_INFO("%@ StartUp event: set estimated start time forward to %@", self,
+                    _estimatedStartTimeFromGeneralDiagnosticsUpTime);
+                _estimatedStartTime = _estimatedStartTimeFromGeneralDiagnosticsUpTime;
+            } else {
+                // If UpTime was not received, reset estimated start time in case of reboot
+                MTR_LOG_INFO("%@ StartUp event: set estimated start time to nil", self);
+                _estimatedStartTime = nil;
+            }
         }
 
         // If event time is of MTREventTimeTypeSystemUpTime type, then update estimated start time as needed
@@ -950,6 +964,26 @@ - (NSArray *)_getAttributesToReportWithReportedValues:(NSArray<NSDictionary<NSSt
                     MTR_LOG_INFO("%@ report %@ value filtered - same values as cache", self, attributePath);
                 }
             }
+
+            // If General Diagnostics UpTime attribute, update the estimated start time as needed.
+            if ((attributePath.cluster.unsignedLongValue == MTRClusterGeneralDiagnosticsID)
+                && (attributePath.attribute.unsignedLongValue == MTRClusterGeneralDiagnosticsAttributeUpTimeID)) {
+                // verify that the uptime is indeed the data type we want
+                if ([attributeDataValue[MTRTypeKey] isEqual:MTRUnsignedIntegerValueType]) {
+                    NSNumber * upTimeNumber = attributeDataValue[MTRValueKey];
+                    NSTimeInterval upTime = upTimeNumber.unsignedLongLongValue; // UpTime unit is defined as seconds in the spec
+                    NSDate * potentialSystemStartTime = [NSDate dateWithTimeIntervalSinceNow:-upTime];
+                    NSDate * oldSystemStartTime = _estimatedStartTime;
+                    if (!_estimatedStartTime || ([potentialSystemStartTime compare:_estimatedStartTime] == NSOrderedAscending)) {
+                        MTR_LOG_INFO("%@ General Diagnostics UpTime %.3lf: estimated start time %@ => %@", self, upTime,
+                            oldSystemStartTime, potentialSystemStartTime);
+                        _estimatedStartTime = potentialSystemStartTime;
+                    }
+
+                    // Save estimate in the subscription resumption case, for when StartUp event uses it
+                    _estimatedStartTimeFromGeneralDiagnosticsUpTime = potentialSystemStartTime;
+                }
+            }
         }
 
         if (shouldReportAttribute) {
diff --git a/src/darwin/Framework/CHIPTests/MTRDeviceTests.m b/src/darwin/Framework/CHIPTests/MTRDeviceTests.m
index f6d6c5d1e0db88..1c2c1520f586d5 100644
--- a/src/darwin/Framework/CHIPTests/MTRDeviceTests.m
+++ b/src/darwin/Framework/CHIPTests/MTRDeviceTests.m
@@ -1543,7 +1543,12 @@ - (void)test017_TestMTRDeviceBasics
                          subscriptionEstablished:^() {
                          }];
 
-    [self waitForExpectations:@[ subscriptionDroppedExpectation, resubscriptionExpectation ] timeout:60 enforceOrder:YES];
+    [self waitForExpectations:@[ subscriptionDroppedExpectation ] timeout:60];
+
+    // Check that device resets start time on subscription drop
+    XCTAssertNil(device.estimatedStartTime);
+
+    [self waitForExpectations:@[ resubscriptionExpectation ] timeout:60];
 
     // Now make sure we ignore later tests.  Ideally we would just unsubscribe
     // or remove the delegate, but there's no good way to do that.
@@ -1557,9 +1562,6 @@ - (void)test017_TestMTRDeviceBasics
     // with data versions) during the resubscribe.
     XCTAssertEqual(attributeReportsReceived, 0);
     XCTAssertEqual(eventReportsReceived, 0);
-
-    // Check that device resets start time on subscription drop
-    XCTAssertNil(device.estimatedStartTime);
 }
 
 - (void)test018_SubscriptionErrorWhenNotResubscribing