diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 20626b2a13b..319ca1a75b0 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6776,6 +6776,21 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
    linkend="datatype-datetime">.
   </para>
 
+  <para>
+   In addition, the usual comparison operators shown in
+   <xref linkend="functions-comparison-op-table"> are available for the
+   date/time types.  Dates and timestamps (with or without time zone) are
+   all comparable, while times (with or without time zone) and intervals
+   can only be compared to other values of the same data type.  When
+   comparing a timestamp without time zone to a timestamp with time zone,
+   the former value is assumed to be given in the time zone specified by
+   the <xref linkend="guc-timezone"> configuration parameter, and is
+   rotated to UTC for comparison to the latter value (which is already
+   in UTC internally).  Similarly, a date value is assumed to represent
+   midnight in the <varname>TimeZone</varname> zone when comparing it
+   to a timestamp.
+  </para>
+
   <para>
    All the functions and operators described below that take <type>time</type> or <type>timestamp</type>
    inputs actually come in two variants: one that takes <type>time with time zone</type> or <type>timestamp