diff --git a/reference/datetime/functions/mktime.xml b/reference/datetime/functions/mktime.xml
index 83fbe7da9d..83a2ba7767 100644
--- a/reference/datetime/functions/mktime.xml
+++ b/reference/datetime/functions/mktime.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.18 $ -->
+<!-- $Revision: 1.19 $ -->
 <!-- splitted from ./en/functions/datetime.xml, last change in rev 1.2 -->
 <refentry id="function.mktime">
  <refnamediv>
@@ -202,9 +202,9 @@ echo strftime("Last day in Feb 2000 is: %d", $lastday);
   &reftitle.notes;
   <caution>
    <para>
-    Negative timestamps are not supported under any known version
-    of Windows.  Therefore the range of valid years includes only 1970
-    through 2038.
+    Before PHP 5.1.0, negative timestamps were not supported under any known
+    version of Windows and some other systems as well. Therefore the range of
+    valid years was limited to 1970 through 2038.
    </para>
   </caution>
  </refsect1>