There are several ways of doing this.
If you are using an Enterprise application, you can set the following options in your weblogic-application.xml:
<prefer-application-packages>
<package-name>org.apache.*</package-name>
<package-name>antlr.*</package-name>
</prefer-application-packages>
And set your package name for joda in there.
Please note that the first option might result in strange behavior from WebLogic.
Note for some reason I can't get the code to work with the XML.