Index: /trunk/doc/manual/en_US/user_AdvancedTopics.xml
===================================================================
--- /trunk/doc/manual/en_US/user_AdvancedTopics.xml	(revision 42326)
+++ /trunk/doc/manual/en_US/user_AdvancedTopics.xml	(revision 42327)
@@ -1542,4 +1542,18 @@
       to VBoxService as well.</para>
     </sect2>
+
+    <sect2 id="disabletimesync">
+      
+      <title>Disabling the Guest Additions time synchronization</title>
+
+      <para>Once installed and started, the VirtualBox Guest Additions will
+        try to synchronize the guest time with the host time. This can be
+        prevented by forbiding the guest service from reading the host
+        clock:</para>
+
+      <screen>VBoxManage setextradata "VM name" "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" 1</screen>
+
+    </sect2>
+
   </sect1>