diff --git a/reference/datetime/reference.xml b/reference/datetime/reference.xml
index 0915369ed6..650793273d 100644
--- a/reference/datetime/reference.xml
+++ b/reference/datetime/reference.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.6 $ -->
+<!-- $Revision: 1.7 $ -->
  <reference id="ref.datetime">
   <title>Date and Time Functions</title>
   <titleabbrev>Date/Time</titleabbrev>
@@ -15,7 +15,10 @@
      <simpara>
       Please keep in mind that these functions are dependent on
       the locale settings of your server. Make sure to take
-      daylight saving time and leap years into consideration when working
+      daylight saving time (use e.g.
+      <literal>$date = strtotime('+7 days', $date)</literal> and not
+      <literal>$date += 7*24*60*60</literal>)
+      and leap years into consideration when working
       with these functions.
      </simpara>
     </note>