This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
That's because the Java classes for the Date used by the session where loaded before the change. Java classes are not hot redeployable, just some application/web servers do redeploys and only in some especific dirs.