Index: oak-core/src/test/java/org/apache/jackrabbit/oak/spi/state/NodeStoreTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/test/java/org/apache/jackrabbit/oak/spi/state/NodeStoreTest.java	(revision cd5ff6d6e7d9e5229037bdf79a83bab3c8941c57)
+++ oak-core/src/test/java/org/apache/jackrabbit/oak/spi/state/NodeStoreTest.java	(revision )
@@ -19,6 +19,7 @@
 package org.apache.jackrabbit.oak.spi.state;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static org.apache.jackrabbit.JcrConstants.JCR_LASTMODIFIED;
 import static org.apache.jackrabbit.oak.api.Type.LONG;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -29,6 +30,7 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Calendar;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
@@ -116,6 +118,55 @@
             b1.setChildNode("n" + k);
             b2.setChildNode("m" + k);
         }
+
+        b1.setChildNode("conflict");
+        b2.setChildNode("conflict");
+
+        store.merge(b1, hook, CommitInfo.EMPTY);
+        store.merge(b2, hook, CommitInfo.EMPTY);
+    }
+
+    @Test
+    public void addExistingNodeJCRLastModified() throws CommitFailedException {
+        CommitHook hook = new CompositeHook(
+            new ConflictHook(JcrConflictHandler.createJcrConflictHandler()),
+            new EditorHook(new ConflictValidatorProvider())
+        );
+
+        NodeBuilder b1 = store.getRoot().builder();
+        NodeBuilder b2 = store.getRoot().builder();
+
+        Calendar calendar = Calendar.getInstance();
+        b1.setChildNode("addExistingNodeJCRLastModified").setProperty(JCR_LASTMODIFIED, calendar);
+        calendar.add(Calendar.MINUTE, 1);
+        b2.setChildNode("addExistingNodeJCRLastModified").setProperty(JCR_LASTMODIFIED, calendar);
+
+        b1.setChildNode("conflict");
+        b2.setChildNode("conflict");
+
+        store.merge(b1, hook, CommitInfo.EMPTY);
+        store.merge(b2, hook, CommitInfo.EMPTY);
+    }
+
+    @Test
+    public void addChangeChangedJCRLastModified() throws CommitFailedException {
+        CommitHook hook = new CompositeHook(
+            new ConflictHook(JcrConflictHandler.createJcrConflictHandler()),
+            new EditorHook(new ConflictValidatorProvider())
+        );
+
+        NodeBuilder b = store.getRoot().builder();
+        Calendar calendar = Calendar.getInstance();
+        b.setChildNode("addExistingNodeJCRLastModified").setProperty(JCR_LASTMODIFIED, calendar);
+        store.merge(b, hook, CommitInfo.EMPTY);
+
+        NodeBuilder b1 = store.getRoot().builder();
+        NodeBuilder b2 = store.getRoot().builder();
+
+        calendar.add(Calendar.MINUTE, 1);
+        b1.setChildNode("addExistingNodeJCRLastModified").setProperty(JCR_LASTMODIFIED, calendar);
+        calendar.add(Calendar.MINUTE, 1);
+        b2.setChildNode("addExistingNodeJCRLastModified").setProperty(JCR_LASTMODIFIED, calendar);
 
         b1.setChildNode("conflict");
         b2.setChildNode("conflict");
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrConflictHandler.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrConflictHandler.java	(revision cd5ff6d6e7d9e5229037bdf79a83bab3c8941c57)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrConflictHandler.java	(revision )
@@ -32,6 +32,7 @@
      */
     public static CompositeConflictHandler createJcrConflictHandler() {
         return new CompositeConflictHandler(ImmutableList.of(
+                new JcrLastModifiedConflictHandler(),
                 new ChildOrderConflictHandler(),
                 new AnnotatingConflictHandler()
         ));
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrLastModifiedConflictHandler.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrLastModifiedConflictHandler.java	(revision )
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/commit/JcrLastModifiedConflictHandler.java	(revision )
@@ -0,0 +1,105 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.jackrabbit.oak.plugins.commit;
+
+import static org.apache.jackrabbit.JcrConstants.JCR_LASTMODIFIED;
+import static org.apache.jackrabbit.util.ISO8601.parse;
+
+import java.util.Calendar;
+
+import org.apache.jackrabbit.oak.api.PropertyState;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.spi.commit.PartialConflictHandler;
+import org.apache.jackrabbit.oak.spi.state.NodeBuilder;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+
+public class JcrLastModifiedConflictHandler implements PartialConflictHandler {
+
+    @Override
+    public Resolution addExistingProperty(NodeBuilder parent, PropertyState ours,
+            PropertyState theirs) {
+        if (isLastModified(ours)) {
+            merge(parent, ours, theirs);
+            return Resolution.MERGED;
+        }
+        return null;
+    }
+
+    @Override
+    public Resolution changeDeletedProperty(NodeBuilder parent, PropertyState ours) {
+        return null;
+    }
+
+    @Override
+    public Resolution changeChangedProperty(NodeBuilder parent, PropertyState ours,
+            PropertyState theirs) {
+        if (isLastModified(ours)) {
+            merge(parent, ours, theirs);
+            return Resolution.MERGED;
+        }
+        return null;
+    }
+
+    private static void merge(NodeBuilder parent, PropertyState ours,
+            PropertyState theirs) {
+        Calendar o = parse(ours.getValue(Type.DATE));
+        Calendar t = parse(theirs.getValue(Type.DATE));
+        // pick & set newer one
+        if (o.before(t)) {
+            parent.setProperty(JCR_LASTMODIFIED, t);
+        } else {
+            parent.setProperty(JCR_LASTMODIFIED, o);
+        }
+    }
+
+    private static boolean isLastModified(PropertyState p) {
+        return JCR_LASTMODIFIED.equals(p.getName());
+    }
+
+    @Override
+    public Resolution deleteDeletedProperty(NodeBuilder parent, PropertyState ours) {
+        return null;
+    }
+
+    @Override
+    public Resolution deleteChangedProperty(NodeBuilder parent, PropertyState theirs) {
+        return null;
+    }
+
+    @Override
+    public Resolution addExistingNode(NodeBuilder parent, String name, NodeState ours, NodeState theirs) {
+        return null;
+    }
+
+    @Override
+    public Resolution changeDeletedNode(NodeBuilder parent, String name, NodeState ours) {
+        return null;
+    }
+
+    @Override
+    public Resolution deleteChangedNode(NodeBuilder parent, String name, NodeState theirs) {
+        return null;
+    }
+
+    @Override
+    public Resolution deleteDeletedNode(NodeBuilder parent, String name) {
+        return null;
+    }
+}