diff --git a/reference/datetime/functions/mktime.xml b/reference/datetime/functions/mktime.xml
index c5e0de1402..4f57848346 100644
--- a/reference/datetime/functions/mktime.xml
+++ b/reference/datetime/functions/mktime.xml
@@ -150,8 +150,7 @@
   <para>
    <function>mktime</function> returns the Unix timestamp of the arguments
    given.
-   If the arguments are invalid, the function returns &false; (before PHP 5.1
-   it returned <literal>-1</literal>).
+   If the arguments are invalid, the function returns &false;.
   </para>
  </refsect1>
 
diff --git a/reference/datetime/functions/strtotime.xml b/reference/datetime/functions/strtotime.xml
index 582eecd887..2ada08e448 100644
--- a/reference/datetime/functions/strtotime.xml
+++ b/reference/datetime/functions/strtotime.xml
@@ -62,8 +62,7 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   Returns a timestamp on success, &false; otherwise. Previous to PHP 5.1.0,
-   this function would return <literal>-1</literal> on failure.
+   Returns a timestamp on success, &false; otherwise.
   </para>
  </refsect1>