New Datetime class problem

Hi all, In our current codebase for PHP5.1 we've a class named 'Datetime' (I suppose a lot of people is in the same situation). I'm wondering if there's any chance to add an ini directive in order to disable the definition of the new class. I mean, we had a lot of PHP4 projects and, with two or three minor changes we got them working in PHP5 (as a matter of fact, we didn't experience almost any BC trouble... It was kind of easy). How could it be more difficult to upgrade from PHP5.1 to PHP5.2? It would be a nightmare too change every date creation, and, of course, the type hints. I'd really like to move to PHP5.2 because it has a lot of really nice things. Thanks. Regards, Mauro.