Added note about new datetime module in Python 2.3.

pep-0249.txt

@@ -572,6 +572,12 @@ Implementation Hints for Module Authors
       Objects/bufferobject.c in the Python source
       distribution.
 
+    * Starting with Python 2.3, module authors can also use the object
+      types defined in the standard datetime module for date/time
+      processing. However, it should be noted that this does not
+      expose a C API like mxDateTime does which means that integration
+      with C based database modules is more difficult.
+        
     * Here is a sample implementation of the Unix ticks based
       constructors for date/time delegating work to the generic
       constructors: