diff --git a/reference/datetime/formats.xml b/reference/datetime/formats.xml
index 4a853149dd..891edc8dd0 100644
--- a/reference/datetime/formats.xml
+++ b/reference/datetime/formats.xml
@@ -508,7 +508,7 @@
      </row>
      <row>
       <entry><literal>ii</literal></entry>
-      <entry>[0-5][0-9]</entry>
+      <entry>[0-5]?[0-9]</entry>
       <entry>"04", "8", "59"</entry>
      </row>
      <row>
@@ -533,8 +533,8 @@
      </row>
      <row>
       <entry><literal>ss</literal></entry>
-      <entry>[0-5][0-9]</entry>
-      <entry>"04", "8", "59"</entry>
+      <entry>([0-5]?[0-9])|60</entry>
+      <entry>"04", "8", "59", "60" (leap second)</entry>
      </row>
      <row>
       <entry><literal>SS</literal></entry>