diff --git a/reference/datetime/formats.xml b/reference/datetime/formats.xml
index 2989e0a90a..45923971f1 100644
--- a/reference/datetime/formats.xml
+++ b/reference/datetime/formats.xml
@@ -890,6 +890,14 @@
     </listitem>
    </orderedlist>
   </note>
+  <note>
+ 		<para>
+ 			Relative month values are calculated based on the length of months that
+ 			they pass through. An example would be "+2 month 2011-11-30", which would
+ 			produce "2012-01-30". This is due to November being 30 days in length, and
+ 			December being 31 days in length, producing a total of 61 days.
+ 		</para>
+  </note>
  </section>
  <!--}}}-->