diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index 35ecd48ed5..3b5b8a65d0 100644
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -2174,17 +2174,17 @@ January 8 04:05:06 1999 PST
          <row>
           <entry><literal>today</literal></entry>
           <entry><type>date</type>, <type>timestamp</type></entry>
-          <entry>midnight today</entry>
+          <entry>midnight (zero hour) today</entry>
          </row>
          <row>
           <entry><literal>tomorrow</literal></entry>
           <entry><type>date</type>, <type>timestamp</type></entry>
-          <entry>midnight tomorrow</entry>
+          <entry>midnight (zero hour) tomorrow</entry>
          </row>
          <row>
           <entry><literal>yesterday</literal></entry>
           <entry><type>date</type>, <type>timestamp</type></entry>
-          <entry>midnight yesterday</entry>
+          <entry>midnight (zero hour) yesterday</entry>
          </row>
          <row>
           <entry><literal>allballs</literal></entry>