Referring to this forum post: http://forums.java.net/node/888356
Hibernate Validator fails with java.lang.ClassNotFoundException: org.joda.time.ReadableInstant when using the @Past and @Future annotations.
A similar bug in JBoss AS 7: https://issues.jboss.org/browse/AS7-1465
The bug is that Hibernate Validator needs Joda Time, but it's not on its classpath.
A possible workaround is to repackage bean-validator.jar with joda-time. This seems to work, but it's far from optimal.